restapi: Remove dynamic searchs from BackendVmResource and BackendVmsResource

Dynamic search is extremely slow. This patch removes the usage of
dynamic search from the BackendVmResource and BackendVmsResource classes.

Change-Id: Ie597cab99334e9be2fbc8e5fe69ddc53392b6d89
Signed-off-by: lzelkha@redhat.com <lzelkha@redhat.com>