[Buffer] Fix the bug that buffer configuration will cause failed logs during warm restart.

[steven-guo-ec]

• What I do:
  Let BufferMgr not execute the entries which are already in APPL_DB after a warm restart.

• Why I did it:
  After warm start, the BufferMgr will set entries into APPL_DB which already exist.
  It will cause bufferorch to do a modification event.
  But, currently, modifying the buffer configuration is not supported in SAI, and it will print error messages.
  The error messages will cause test cases to fail.

• How I verify it:
  With this enhancement, the syslog will not appear the error messages about Buffer during a warm restart.

[stephenxs]

@steven-guo-ec
can you please elaborate on which buffer attributes are not supported in SAI?
IMO buffer orch will not set create-only attributes

[prsunny]

Please add VS tests

[steven-guo-ec]

SAI_BUFFER_POOL_ATTR_SIZE and SAI_BUFFER_PROFILE_ATTR_BUFFER_SIZE is not supported to set after they were created, they can be configured only when creating them.

[stephenxs]

SAI_BUFFER_POOL_ATTR_SIZE and SAI_BUFFER_PROFILE_ATTR_BUFFER_SIZE is not supported to set after they were created, they can be configured only when creating them.

Thanks. But this does not comply with SAI definition. Check SAI_BUFFER_POOL_ATTR_SIZE and SAI_BUFFER_PROFILE_ATTR_RESERVED_BUFFER_SIZE for details.
So IMO this should be fixed by vendor SAI.