advance submodule (#15264)

Why I did it
69abbc3c - (HEAD, origin/master, origin/HEAD) Revert "[GCU] Complete RDMA Platform Validation Checks [device][platform] Update Inventec new platform d6356 #2791" DellEMC S6100 Watchdog Support #2854 (8 minutes ago)
4fead896 - [sonic-package-manager] fix CLI plugin compatibility issue [sonic-utilities] advance submodule head to latest #2842 (27 hours ago)
db61efca - [vlan][dhcp_relay] Clear dhcpv6 relay counter while deleting vlan ([201811] [services] Restart SwSS service upon unexpected critical process exit #2852) (33 hours ago)
d5544b4a - [config] Generate sysinfo as needed when override config ([minigraph]: Add mirror type v6 condition #2836) (6 days ago)
f258e2a3 - [GCU] Complete RDMA Platform Validation Checks ([device][platform] Update Inventec new platform d6356 #2791) (6 days ago)
b4f4e63e - Revert "Revert frr route check ([mlnx] fix url inconsistency in fw.mk #2761)" (Support TACACS Accounting #2762) (7 days ago)
3d89589f - Update pcieutil error message on loading common pcie module (Enable Debugs in BCM Kernel-bde and Knet Modules #2786) (11 days ago)
e6aacd37 - Update TRANSCEIVER_INFO table after CDB FW upgrade (Remove unused packages in docker images and host (#2807) #2837) (2 weeks ago)
33d665c4 - replace shell=True, replace xml, and replace exit() ([mellanox-simx] add ability to build simx-compatiable image #2664) (2 weeks ago)
9e510a83 - [chassis][voq[Add "config fabric port ..." commands and tests. (Watchdog enable/disable in DellEMC S6100  #2730) (2 weeks ago)
aeb0dbc1 - Fix the invalid variable issue when set-fips in uboot (fix bug in file sonic-cfggen #2834) (3 weeks ago)
1e73632d - [test]: add UT coverage for GCU (Feed device info to orchagent process #2818) (3 weeks ago)
3a9995b6 - [config]Support multi-asic Golden Config override with fix ([mellanox] Update Mellanox MFT packedge #2825) (3 weeks ago)
3fb32588 - Revert "[chassis]: remote cli commands infra for sonic chassis ([mellanox] add makefiles to build Mellanox SDK from sources  #2701)" ([dhcp_relay] Base DHCP Relay Docker container on Debian Stretch #2832) (3 weeks ago)
2ffe6e37 - [show][mlnx] replace shell=True, replace xml (Add support of HwSKU Mellanox-SN2700-C28D8 #2700) (3 weeks ago)
a5091bba - [sonic_sku_create] remove shell=True, replace exit() with sys.exit() (removed exec from script which that prevents the further lines to be … #2816) (3 weeks ago)
71ef4f16 - [build] Fix base OS compilation issue caused by incompatibility with requests >= 2.29.0. ([201811][sairedis][utilities] advance sub module heads #2830) (3 weeks ago)
1097373b - [show] Added alias interface mode support for 'show interfaces counters ...' command ([kernel]: update sonic kernel to 4.9.0-8-2 #2468) (4 weeks ago) <Julian Chang - TW>
589375fc - correctly parsing complete ipv6 vnet info ([201811][mellanox] Update Mellanox FW version to 13.1910.0928 #2827) (4 weeks ago)
634ac77c - LAG keepalive script to reduce lacp session wait during warm-reboot (Set proper hostname on containers startup #2806) (4 weeks ago)
331c9de0 - [config]: Dynamically start and stop ndppd ([Arista] Add QoS needed files for Arista 7170 #2814) (4 weeks ago)
d1f307d0 - [GCU]Fix rdma check failure ([device/celestica]: Add fwutil #2824) (4 weeks ago)
ce81a340 - Revert "[config]Support multi-asic Golden Config override (Before issue “sonic-clear counters”, “show interface counters” result not complete #2738)" ([BGP docker]: start bgp_eoiu_mark service to populate bgp eoiu marker… #2823) (4 weeks ago)
61e0e810 - Added platform plugin support in load_minigraph ([db migrator] migrate the DB to latest schema when needed #2808) (4 weeks ago)
d4355a96 - Change default CDB run mode to non-hitless (Revert "Watchdog enable/disable in DellEMC S6100 " #2817) (4 weeks ago)
88ffb167 - [config]config reload should generate sysinfo if missing ([Mellanox] Update SAI #2778) (4 weeks ago)
7443b9e5 - [sonic-package-manager] support extension with multiple YANG modules (dhcp_relay service stopped with "systemctl stop swss" but not restarted with "systemctl restart swss" #2752) (4 weeks ago)
522c3a9e - [sonic-package-manager] add support for multiple CLI plugin files (Updated Makefile infrastructure to build debug images. #2753) (4 weeks ago)
b38fcfd1 - [show][muxcable] fix show mux hwmode muxdirection RC (syncd-rpc.mk: Fix stretch dockers build failure #2812) (5 weeks ago)
7e24463f - [chassis]: remote cli commands infra for sonic chassis ([mellanox] add makefiles to build Mellanox SDK from sources  #2701) (6 weeks ago)
bee593e4 - [DPB]Fixing typo in config breakout output ([submodule update]: Quagga bgpd crash fix #2802) (6 weeks ago)
ada603c5 - [config]Support multi-asic Golden Config override (Before issue “sonic-clear counters”, “show interface counters” result not complete #2738) (6 weeks ago)
88a7daa8 - [show][barefoot] replace shell=True ([teamd] retry creating team_port after interface info changed #2699) (6 weeks ago)
5e99edb5 - [sonic_package_manager] replace shell=True (Upgrade Mellanox HW-MGMT: fix high CPU utilization issue #2726) (6 weeks ago)
b547bb45 - [acl-loader] Only add default deny rule when table is L3 or L3V6 ([201811] [radvd] Build radvd from source; Patch so as not to treat out-of-range MTU as an error #2796) (6 weeks ago)