Remove unused method 'is_key_value_present()'

The following method is not used.
  is_key_value_present() in cinder/volume/volume_types.py

Change-Id: If1ecd22f2cfb758f0e9f7c6b730727559e9dcdf0
Add support for retype in Storwize/SVC driver

In Storwize/SVC, retype can be handled by a few cases:
1. The change may just require setting an option on the volume
2. The change may require moving the data in the same pool (e.g.,
   compression)
3. The scheduler may have chosen a different pool virtualized by the
   same Storwize or SVC, in which case we move the data as in #2

Implements: blueprint storwize-svc-retype

Change-Id: Ic2ed17bce56b5ea65e1596acfa85720cf4818fa8
Merge "Add support for retype in Storwize/SVC driver"
Merge "Remove unused method 'is_key_value_present()'"