VMware: Add retype to list of supported operations

Commit 86591a24d48fe19be427b5a8981821fcdb85bb37 added support for
retype API in VMDK driver. Retype allows the user to change the
volume type associated with a volume. This patch updates the list
of supported operations by VMDK driver to include retype.

Change-Id: I4610b86fdf635f26dcdd6ad873caa29b5070e155
Merge "VMware: Add retype to list of supported operations"