VMware: Implement vmdk extend_volume

Add the API implementation of extend_volume for the VMware
vmdk driver.

Change-Id: Idf09c9e9cf015c78c1c5e91c05b897e3e9b7c006
Closes-Bug: #1232172
Merge "VMware: Implement vmdk extend_volume"
(Test commit) Change README to reflect Jio's fork of Cinder

Change-Id: I3f26c0a736e63725aec24ca2fa12c707b8e6460f