https://bugzilla.redhat.com/show_bug.cgi?id=1332019

This function will essentially be a wrapper to virStorageVolInfo in order
to provide a mechanism to have the "physical" size of the volume returned
instead of the "allocation" size. This will provide similar capabilities to
the virDomainBlockInfo which can return both allocation and physical of a
domain storage volume.

NB: Since we're reusing the _virStorageVolInfo and not creating a new
_virStorageVolInfoFlags structure, we'll need to generate the rpc APIs
remoteStorageVolGetInfoFlags and remoteDispatchStorageVolGetInfoFlags
(although both were originally created from gendispatch.pl and then
just copied into daemon/remote.c and src/remote/remote_driver.c).

The new API will allow the usage of a VIR_STORAGE_VOL_GET_PHYSICAL flag
and will make the decision to return the physical or allocation value
into the allocation field.

In order to get that physical value, virStorageBackendUpdateVolTargetInfoFD
adds logic to fill in physical value matching logic in qemuStorageLimitsRefresh
used by virDomainBlockInfo when the domain is inactive.
Signed-off-by: NJohn Ferlan <jferlan@redhat.com>