core: GetVmTemplatesByStoragePoolIdQuery did not return anything

The problem was a regression introduced in
88756e3897ba467eb50055a7dda0c1afb11295d0
due to which an incorrect DB call was called.

Fixed by implementing the proper DB call (getAllForStoragePool).

Change-Id: I62627ca3a9942901abda1ee7522e8f0de1f29764
Signed-off-by: Tomas Jelinek <tjelinek@redhat.com>