core:ExportVm.doesStorageDomainhaveSpaceForRequest

Removed
ExportVmCommand.doesStorageDomainhaveSpaceForRequest(StorageDomain,
long). It's exactly identical to the method it overrides in
StorageDomainCommandBase, and is thus redundant.

Change-Id: Ia267125106c6465c064719c2718053644b556195
Signed-off-by: Allon Mureinik <amureini@redhat.com>
core: Removed unused method in MoveOrCopyDisk

Removed
MoveOrCopyDiskCommand.doesStorageDomainHaveSpaceForRequest(long), which
is not used anywhere in the code.

Change-Id: I12e0ed58810bf87342cc06db4b7cec4c527b6ff5
Signed-off-by: Allon Mureinik <amureini@redhat.com>
core: RemoveDiskCommand: only validate images once

RemoveDiskCommand.canRemoveVmImageDisk() called
ImageHandler.PerformImagesChecks in a loop, for each VM attached to the
disk.

Since the VM checks have been extracted from
ImageHandler.PerformImagesChecks in commit
69b515c3a30b0185f05b3b7d3451806f2b5b86cb, this is no longer required,
can the validation can be called a single time.

Change-Id: I8c0408db32415785bfe36d144b08a6f6c9f0aefc
Signed-off-by: Allon Mureinik <amureini@redhat.com>