Update sonic-py-swsssdk. (sonic-net#7889)

Update sonic-py-swsssdk submodule to include below commits:
6be76f45 Add missing functions to be on par with swsscommon. (sonic-net#107)
64232a0 (master) [CI] Setup proper Azp (sonic-net#106)
9d019b0 [ci]: Set up CI with Azure Pipelines (sonic-net#102)
fa760c4 Fix bug: use instance variable instead of class variable in ConfigDBConnector (sonic-net#99)
Signed-off-by: Suvarna Meenakshi <[email protected]>