load_minigraph consistently fails on S6100 T0 and T1 testbeds.

[vaibhavhd]

Description

load_minigraph fails with errors seen in starting the Telemetry service.
The telemetry service throws an error as it depends on /var/platform dir's presence.

In turn /var/platform dir is not created because of an error seen in rc.local file and the mkdir step is never executed:
https://github.com/Azure/sonic-buildimage/blob/master/files/image_config/platform/rc.local#L361

rc.local is wrongly entering NOS to SONiC migration section of code, when this is merely SONiC to SONiC upgrade. I believe that this is a regression caused by #5234

Errors seen in rc.local:

Oct  1 21:03:20 sonic rc.local[447]: + log_migration ERROR: /mnt/nos_migration/mgmt_interface.cfg not found!
Oct  1 21:03:20 sonic rc.local[447]: + log_migration ERROR: /mnt/nos_migration/mgmt_interface.cfg not found!
Oct  1 21:03:20 sonic rc.local[447]: + echo ERROR: /mnt/nos_migration/mgmt_interface.cfg not found!
Oct  1 21:03:20 sonic rc.local[447]: + echo ERROR: /mnt/nos_migration/mgmt_interface.cfg not found!

Oct  1 21:04:05 sonic rc.local[447]: + mount /mnt/onie-boot
Oct  1 21:04:05 sonic rc.local[447]: + mount /mnt/onie-boot
Oct  1 21:04:05 sonic rc.local[447]: mount: can't find /mnt/onie-boot in /etc/fstab
Oct  1 21:04:05 sonic rc.local[447]: mount: can't find /mnt/onie-boot in /etc/fstab
Oct  1 21:04:06 sonic rc.local[447]: + . /mnt/onie-boot/onie/grub.d/50_onie_grub
Oct  1 21:04:06 sonic rc.local[447]: + . /mnt/onie-boot/onie/grub.d/50_onie_grub
Oct  1 21:04:06 sonic rc.local[447]: /etc/rc.local: 346: .: Can't open /mnt/onie-boot/onie/grub.d/50_onie_grub
Oct  1 21:04:06 sonic rc.local[447]: /etc/rc.local: 346: .: Can't open /mnt/onie-boot/onie/grub.d/50_onie_grub

Steps to reproduce the issue:

1. Install a new latest image
2. Execute command sudo config load_minigraph -y
3. The last step would fail as:
   Executing restart of service telemetry... Job for telemetry.service failed because the control process exited with error code.

Describe the results you received:

Oct  1 17:11:18.666479 str-s6100-acs-5 INFO telemetry.sh[19002]: Creating new telemetry container with HWSKU Force10-S6100
Oct  1 17:11:18.807194 str-s6100-acs-5 INFO dhcp_relay.sh[18936]: dhcp_relay
Oct  1 17:11:18.825976 str-s6100-acs-5 INFO systemd[1]: Started DHCP relay container.
Oct  1 17:11:18.833017 str-s6100-acs-5 INFO hostcfgd: Running cmd: 'sudo systemctl enable pmon.service'
Oct  1 17:11:18.897429 str-s6100-acs-5 INFO telemetry.sh[19002]: Error response from daemon: invalid mount config for type "bind": bind source path does not exist: /var/platform/
Oct  1 17:11:18.902717 str-s6100-acs-5 INFO telemetry.sh[19002]: Failed to docker run
Oct  1 17:11:18.907558 str-s6100-acs-5 ERR systemd[1]: Failed to start Telemetry container.
Oct  1 17:11:18.936166 str-s6100-acs-5 ERR config[15832]: Failed to execute restart of service telemetry with error 1

Describe the results you expected:
config load_minigraph should pass.