utils: add isOvirtNode function.

Change-Id: I82207f674f9d1854f9fdddd0804de611073a794c
Signed-off-by: Alon Bar-Lev <alonbl@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/28486
Tested-by: mooli tayer <mtayer@redhat.com>
Reviewed-by: Yaniv Bronhaim <ybronhei@redhat.com>
Reviewed-by: Dan Kenigsberg <danken@redhat.com>