start mock for block storage

[tawalton]

This is the beginning of the cinder plugin. It has one route to get the list of volumes, which addresses issue, #485

[codecov-io]

Current coverage is 99.16%

Merging #489 into master will increase coverage by +0.01% as of 0e99812

@@            master    #489   diff @@
======================================
  Files           68      70     +2
  Stmts         4165    4195    +30
  Branches       625     627     +2
  Methods          0       0       
======================================
+ Hit           4130    4160    +30
  Partial         25      25       
  Missed          10      10       

Review entire Coverage Diff as of 0e99812

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[lekhajee]

+1