Oliver/HFX-771:CA-98944: Replaced potentially lots of db calls (one per VBD) by two big get_internal_where calls

Signed-off-by: Vincent Bernardoff <vincent.bernardoff@citrix.com>

Conflicts:

	ocaml/test/OMakefile
	ocaml/test/suite.ml
	ocaml/xapi/xapi_test_common.ml