VMware: fix missing datastore regex with ESX driver

When using shared datastore and the ESX driver the administrator
is unable to indicate which datastore to use.

Note: there were extensive tests added for the VC driver for the
regex support. These are invoked by passing the flag for the regex
when the ESX driver is created.

Change-Id: Ifb0a4a8df2b26f3521b1301462d1f2c3eeba5c14
Closes-bug: #1246206
Merge "VMware: fix missing datastore regex with ESX driver"