unity code rebase

[tanjiangyu-ghca]

What this PR does / why we need it:

Which issue this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close that issue when PR gets merged): fixes #

Special notes for your reviewer:

Release note:

[codecov]

Codecov Report

Merging #531 (cee1edb) into unity_host (e6fac2a) will increase coverage by 0.29%.
The diff coverage is 74.25%.

@@              Coverage Diff               @@
##           unity_host     #531      +/-   ##
==============================================
+ Coverage       70.55%   70.84%   +0.29%     
==============================================
  Files             180      182       +2     
  Lines           18929    20488    +1559     
  Branches         2786     3104     +318     
==============================================
+ Hits            13355    14515    +1160     
- Misses           4722     4981     +259     
- Partials          852      992     +140     

Impacted Files	Coverage Δ
delfin/drivers/fake_storage/__init__.py	94.40% <0.00%> (ø)
delfin/test.py	59.69% <0.00%> (ø)
delfin/drivers/hitachi/vsp/rest_handler.py	40.40% <21.73%> (-1.74%)	⬇️
delfin/drivers/dell_emc/unity/rest_handler.py	44.66% <33.33%> (-2.19%)	⬇️
delfin/drivers/netapp/dataontap/netapp_handler.py	64.10% <44.82%> (-1.52%)	⬇️
delfin/drivers/hpe/hpe_3par/rest_handler.py	35.43% <46.66%> (+1.50%)	⬆️
delfin/drivers/utils/tools.py	64.65% <60.00%> (-6.06%)	⬇️
...rivers/dell_emc/vnx/vnx_block/component_handler.py	76.01% <62.22%> (-5.38%)	⬇️
delfin/drivers/hitachi/vsp/vsp_stor.py	68.55% <65.16%> (-1.97%)	⬇️
delfin/drivers/dell_emc/unity/unity.py	68.08% <67.24%> (-0.95%)	⬇️
... and 21 more