VMware: clean up unnecessary help message of options

Configuration options were grouped into [vmware]. So we don't need
point out that these options are used only for vmwareapi.VMwareESXDriver
or vmwareapi.VMwareVCDriver. This patch also corrects docstring for
vCenter related classes.

Change-Id: I77d95250ce1351bad60664ec7313d8e18d76332a
Merge "VMware: clean up unnecessary help message of options"