WIP: Add centralized manager support to delfin

[joseph-v]

What this PR does / why we need it: Add centralized manager support to delfin

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[bot]]

Codecov Report

Merging #559 (9ddf1a8) into master (73fe3a1) will decrease coverage by 2.29%. The diff coverage is 29.97%.

:exclamation: Current head 9ddf1a8 differs from pull request most recent head 4ce30fa. Consider uploading reports for the commit 4ce30fa to get more accurate results

@@            Coverage Diff             @@
##           master     #559      +/-   ##
==========================================
- Coverage   72.13%   69.84%   -2.30%     
==========================================
  Files         141      140       -1     
  Lines       12211    10865    -1346     
  Branches     1446     1216     -230     
==========================================
- Hits         8809     7589    -1220     
+ Misses       2909     2902       -7     
+ Partials      493      374     -119     

Impacted Files	Coverage Δ
delfin/drivers/helper.py	63.63% <9.09%> (-36.37%)	:arrow_down:
delfin/drivers/api.py	65.21% <9.67%> (-20.50%)	:arrow_down:
delfin/api/v1/access_info.py	78.04% <18.18%> (-21.96%)	:arrow_down:
delfin/db/sqlalchemy/api.py	77.37% <19.14%> (-2.65%)	:arrow_down:
delfin/drivers/fake_storage/__init__.py	84.48% <25.00%> (-2.01%)	:arrow_down:
delfin/task_manager/tasks/resources.py	78.71% <25.00%> (-3.88%)	:arrow_down:
delfin/api/v1/centralized_managers.py	29.11% <29.11%> (ø)
delfin/api/views/centralized_managers.py	42.85% <42.85%> (ø)
delfin/db/api.py	92.79% <50.00%> (-2.02%)	:arrow_down:
delfin/drivers/driver.py	66.66% <50.00%> (-0.61%)	:arrow_down:
... and 28 more