VMware: Change disk type thick to lazyZeroedThick

The VMDK driver creates a lazyZeroedThick disk when the extra spec
value for vmware:vmdk_type is thick. The current documentation
uses the terminology 'thick' disk instead of 'lazyZeroedThick' disk.

Change-Id: Ie64d814578fbc0497b3c6afc378573ac3dfafb2a
Closes-Bug: #1371036
Merge "VMware: Change disk type thick to lazyZeroedThick"