Bug 5478 - northbound: improve 404 check on update/delete

Bug 5478 - northbound: improve 404 check on update/delete

canDelete should not be called on deletion on non-exist resource. Instead,
it should return 404 immediately without calling I*Aware.
This patch improves 404 check by adds missing 404 check by checking
return value on update and delete with a bit clean up.

Change-Id: Ia4fe068540022f687d942204f3b243ccbcbac578
Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>