[202205] Enhance orchagent and buffer manager in error handling (#2414)

[stephenxs]

Cherry-pick #2414 to 202205.

What I did
Enhance orchagent and buffer manager

• Buffer manager: do not insert buffer queue into cache if the profile is illegal, which prevents an empty string from being inserted into APPL_DB during initialization.
• orchagent: handle the case that a field referencing other objects is an empty string.
  There had been such logic that was broken by a PR last year.

Signed-off-by: Stephen Sun stephens@nvidia.com

Why I did it
Enhance the error handling logic.
In most cases, a user will not encounter such scenarios in a production environment because it's the front-ends' (eg. CLI) responsibility to identify the wrong configuration and prevent them from being inserted to CONFIG_DB.
However, in some cases, like a wrong config_db.json composed and copied to the switch, front-ends can not prevent that.

How I verified it
Manual and mock tests.

Details if related
For the improvement in buffer manager:

• previously, the logic was:
  • declare a reference portQueue to m_portQueueLookup[port][queues] and then assign fvValue(i) to portQueue.running_profile_name
  • But [] operation on C++ map has a side-effect -- it will insert a new element into the map if there wasn't one. In case the validation check in checkBufferProfileDirection failed and there was not one in the map, the portQueue.running_profile_name will keep empty. This is not what we want.
  • In case there was an item configured in the map, we should not remove it on failure because we want to prevent the user from being affected by misconfiguration and alert user to correct the error. There is log in checkBufferProfileDirection
• Now it is improved in this way:
  • Avoid using reference and initialize m_portQueueLookup[port][queues] only if there is a valid egress profile configured