[swss] submodule update

9f6efa0 [port/buffer] introduce a sync mechanism to protect port
PG/queue from changes under PFC storm (sonic-net#1143)
823e426 [aclorch] Enable DSCP rules on IPv6 mirror tables (sonic-net#1146)
b8745f8 [bitmap_vnet]: Fix removal flow for tunnel route (sonic-net#1139)
03be983 Increase ip2me CIR/CBR for faster in-band file transfers (sonic-net#1000)
a4a1d3b [vnet]: Update VNET route table size to 40K for BITMAP
implementation (sonic-net#1132)
efe142a Fix bug: Wrong condition for mac address (sonic-net#1142)
7bf63a0 [teammgrd]during warm-reboot teamd need to recover system-id
from saved lacp-pdu (sonic-net#1003)
8b4cfb6 Cleanup configure.ac from BFN specific code (sonic-net#1133)
b931751 [teamsyncd]: Add retry logic in teamsyncd to avoid team handler
init failure (sonic-net#854)

Signed-off-by: Stepan Blyschak <stepanb@mellanox.com>