phosphor-objmgr: remove pending associations by service

If Service A has an association on Object X with Object Y (which comes
from Service C), and Service B also has an association definition for
Object X, there is a scenario where the X-Y association will not be
created, even though both objects are present in the D-Bus tree.

This change matches with the service while removing the pending
association for an object. Only the pending association introduced by
the service which removes the object/interface will be erased.

The change is accepted in Upstream.

Tested: Unit Tested. Also tested in a machine and checked all the
associations were created correctly following the above steps.

Fusion-Link:
platform5: https://fusion2.corp.google.com/741e9e05-9d22-33b3-ac0f-17610fe1ddfd
platform15: https://fusion2.corp.google.com/1c47d1b1-4b57-3df4-a172-acab8f30eb99
platform18: https://fusion2.corp.google.com/755b43f1-f9e8-32a5-880c-2d57bb0ad784
platform17: https://fusion2.corp.google.com/63ef3f9b-ad59-3528-8c54-4a986f05c649
platform11+ext: https://fusion2.corp.google.com/2fba6019-1d63-35b3-bb09-535621a27da4
platform11: https://fusion2.corp.google.com/86d39ef0-61aa-38bf-a34c-781793592b2b

Platforms-Affected: All
Google-Bug-Id: 488925115
Change-Id: I79bc7cfcf782a6aeee68370a3463ca84c124995e
Signed-off-by: Munawar Hussain <munawarhussain@google.com>
(cherry picked from commit 74ace72c37ecdbcfc11fd216754f08bef490fa9a)