core: Remove unused VmLockCommad

VmLockCommand is not used anywhere in the codebsae, and can thus be
removed.

This patch removes:
1. The VmLockCommand class
2. Its corresponding constant in VdcActionType
3. The VmLockVDSCommand class, only used by VmLockCommand
4. The corresponding constant in VDSCommantType
5. The VmLockVDSCommandParameters class, only used by VmLockVDSCommand
6. The vmLock method in IVdsServer/VdsServerConnector/VdsServerWrapper
   which was only used by VmLockVDSCommand

Change-Id: I00ffd5da1a93271cd4cc31de0f72953d78e4d62a
Signed-off-by: Allon Mureinik <amureini@redhat.com>