Unit test cases for block volume and block volume snapshot

[nguptaopensds]

What type of PR is this?

Uncomment only one /kind <> line, hit enter to put that in a new line, and remove leading whitespace from that line:

/kind new feature
/kind bug fix
/kind cleanup
/kind revert change
/kind design
/kind documentation

/kind enhancement

What this PR does / why we need it:
Adding unit test cases for block volumes

Which issue(s) this PR fixes:
#1270

Fixes #

Test Report Added?:

Uncomment only one /kind <> line, hit enter to put that in a new line, and remove leading whitespace from that line:

/kind TESTED

/kind NOT-TESTED

Test Report:

Special notes for your reviewer:

[codecov]

Codecov Report

Merging #1299 into master will decrease coverage by 1.80%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1299      +/-   ##
==========================================
- Coverage   41.48%   39.67%   -1.81%     
==========================================
  Files          53       53              
  Lines        7752     6966     -786     
==========================================
- Hits         3216     2764     -452     
+ Misses       4021     3662     -359     
- Partials      515      540      +25     

Impacted Files	Coverage Δ
client/volume.go	62.31% <0.00%> (-8.40%)	⬇️
client/fileshare.go	65.95% <0.00%> (-7.22%)	⬇️
client/dock.go	42.85% <0.00%> (-7.15%)	⬇️
client/pool.go	42.85% <0.00%> (-7.15%)	⬇️
client/host.go	61.11% <0.00%> (-6.98%)	⬇️
client/version.go	46.15% <0.00%> (-6.79%)	⬇️
client/profile.go	55.55% <0.00%> (-6.42%)	⬇️
pkg/api/policy/policy.go	25.88% <0.00%> (-5.19%)	⬇️
pkg/api/controllers/version.go	65.21% <0.00%> (-4.02%)	⬇️
pkg/api/controllers/base.go	76.74% <0.00%> (-3.26%)	⬇️
... and 43 more

[kumarashit]

LGTM