config reload reports SwSS container not running for multi-asic

[anamehra]

Description

On a multi-asic system, config reload CLI does not work wihtout -f option.
root:/home/admin# config reload
SwSS container is not ready. Retry later or use -f to avoid system checks

The issue is that config/main.py checks for swss.service status even for multi-asic system. On a multi-asic system, there is no swss.service but multi-instance versions like swss@0.service etc.

_swss_ready should be fixed to handle the multi-asic scenarios.

Steps to reproduce the issue:

1. Boot multi asic system
2. check docker ps to check all expected dockers running
3. config reload

Describe the results you received:

SwSS container is not ready. Retry later or use -f to avoid system checks

Describe the results you expected:

config reload should work without -f option

Output of show version:

(paste your output here)

Output of show techsupport:

(paste your output here or download and attach the file here )

Additional information you deem important (e.g. issue happens only occasionally):

[anamehra]

@abdosi

[abdosi]

@SuvarnaMeenakshi working on this.

cc @rlhui