Fix code issue when SonicV2Connector.get() return None.
#### Why I did it
When database key does not exist, SonicV2Connector.get() will return None.
Code will break if not check return value.
#### How I did it
Check SonicV2Connector.get() return value before use it.
#### How to verify it
Pass all E2E test case.
#### Why I did it
Update scripts in sonic-buildimage from py-swsssdk to swsscommon
#### How I did it
Replace swsssdk with swsscommon in alphanetworks devices code.
#### How to verify it
Pass all E2E test case
#### Which release branch to backport (provide reason below if selected)
<!--
- Note we only backport fixes to a release branch, *not* features!
- Please also provide a reason for the backporting below.
- e.g.
- [x] 202006
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- [ ] 201811
- [ ] 201911
- [ ] 202006
- [ ] 202012
- [ ] 202106
- [ ] 202111
- [ ] 202205
#### Description for the changelog
Replace swsssdk with swsscommon in alphanetworks devices code.
#### Link to config_db schema for YANG module changes
<!--
Provide a link to config_db schema for the table for which YANG model
is defined
Link should point to correct section on https://github.com/Azure/sonic-buildimage/blob/master/src/sonic-yang-models/doc/Configuration.md
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#### A picture of a cute animal (not mandatory but encouraged)
Submodule updates include the following commits:
* src/sonic-utilities 9dc58ea...f9eb739 (18):
> Remove unnecessary calls to str.encode() now that the package is Python 3; Fix deprecation warning (#1260)
> [generate_dump] Ignoring file/directory not found Errors (#1201)
> Fixed porstat rate and util issues (#1140)
> fix error: interface counters is mismatch after warm-reboot (#1099)
> Remove unnecessary calls to str.decode() now that the package is Python 3 (#1255)
> [acl-loader] Make list sorting compliant with Python 3 (#1257)
> Replace hard-coded fast-reboot with variable. And some typo corrections (#1254)
> [configlet][portconfig] Remove calls to dict.has_key() which is not available in Python 3 (#1247)
> Remove unnecessary conversions to list() and calls to dict.keys() (#1243)
> Clean up LGTM alerts (#1239)
> Add 'requests' as install dependency in setup.py (#1240)
> Convert to Python 3 (#1128)
> Fix mock SonicV2Connector in python3: use decode_responses mode so caller code will be the same as python2 (#1238)
> [tests] Do not trim from PATH if we did not append to it; Clean up/fix shebangs in scripts (#1233)
> Updates to bgp config and show commands with BGP_INTERNAL_NEIGHBOR table (#1224)
> [cli]: NAT show commands newline issue after migrated to Python3 (#1204)
> [doc]: Update Command-Reference.md (#1231)
> Added 'import sys' in feature.py file (#1232)
* src/sonic-py-swsssdk 9d9f0c6...1664be9 (2):
> Fix: no need to decode() after redis client scan, so it will work for both python2 and python3 (#96)
> FieldValueMap `contains`(`in`) will also work when migrated to libswsscommon(C++ with SWIG wrapper) (#94)
- Also fix Python 3-related issues:
- Use integer (floor) division in config_samples.py (sonic-config-engine)
- Replace print statement with print function in eeprom.py plugin for x86_64-kvm_x86_64-r0 platform
- Update all platform plugins to be compatible with both Python 2 and Python 3
- Remove shebangs from plugins files which are not intended to be executable
- Replace tabs with spaces in Python plugin files and fix alignment, because Python 3 is more strict
- Remove trailing whitespace from plugins files
