vmware:Ignore inaccessible/inMaintenance datastore

The vmdk driver uses the number of hosts connected to a datastore as one
of the criteria for selecting a datastore for volume creation. It might
incorrectly consider a host to which the datastore is inaccessible while
computing the number of connected hosts. This is because, the driver
sometimes uses the aggregated accessible status of a datastore while
determining its accessibility to a host. Also, the driver is ignoring
the maintenance status of the datastore and might create a volume in a
datastore which is entering maintenance or already in maintenance. This
change fixes these issues in datastore filtering.

Change-Id: Ibd5c1865d42638a735fd588e9c10e8f714c9c030
Closes-Bug: #1291346
Closes-Bug: #1291291
Merge "vmware:Ignore inaccessible/inMaintenance datastore"