Remove double.doubleToLongBits from VM.hashCode

patch http://gerrit.ovirt.org/#/c/14965 added hashCode to VM,
but GWT doesn't support doubleToLongBits() method.

Change-Id: I4b5f9afabb645ece870df409e5959d151d1952e1
Signed-off-by: Shahar Havivi <shavivi@redhat.com>