Fix lb-healthmonitor-update to work with correct object

Previously in case specified id was incorrect, client fetched
healthmonitors trying to filter them by name which had no effect since
healthmonitor object doesn't have name attribute.
The patch fixes the behavior by making lb-healthmonitor-update rely
on finding resource by id, not by name-or-id

Change-Id: Iade1c3270ec6c60362dd9a9b5e2ffdb0ad9430c1
Closes-Bug: #1245859
Merge "Fix lb-healthmonitor-update to work with correct object"