Add one more test for ssync_receiver
Add one more test for ssync_receiver

To prevent 409 conflict on a primary node during ssyncing,
ssync-receiver should add x-ssync-backend-frag-index generated from
x-ssync-backend-node-index of the SSYNC replication request header.
The change is done by previous work[1], but we need more test for that.

This patch addes one more assertion if the x-ssync-backend-frag-index
is in the ssync subrequest correctly.

*BONUS*
Fix some weird mock and add some sanities.

1: https://review.openstack.org/#/c/191521/

Change-Id: I27aff713c69017c0bc4c60b4833184e1285595d7

williamthegrey/swift,larsbutler/swift,notmyname/swift,clayg/swift,gold3bear/swift,mjwtom/swift,daasbank/swift,gold3bear/swift,matthewoliver/swift,hurricanerix/swift,prashanthpai/swift,openstack/swift,thiagodasilva/swift,aerwin3/swift,revoer/keystone-8.0.0,hbhdytf/mac,swiftstack/swift,redbo/swift,smerritt/swift,clayg/swift,psachin/swift,Akanoa/swift,notmyname/swift,tipabu/swift,nadeemsyed/swift,notmyname/swift,zackmdavis/swift,smerritt/swift,Akanoa/swift,zackmdavis/swift,hbhdytf/mac2,prashanthpai/swift,dencaval/swift,rackerlabs/swift,openstack/swift,nadeemsyed/swift,mjzmjz/swift,shibaniahegde/OpenStak_swift,shibaniahegde/OpenStak_swift,rackerlabs/swift,aerwin3/swift,redhat-openstack/swift,revoer/keystone-8.0.0,smerritt/swift,daasbank/swift,takeshineshiro/swift,openstack/swift,dencaval/swift,thiagodasilva/swift,clayg/swift,tipabu/swift,psachin/swift,hbhdytf/mac2,larsbutler/swift,matthewoliver/swift,psachin/swift,swiftstack/swift,hurricanerix/swift,bkolli/swift,notmyname/swift,tipabu/swift,bradleypj823/swift,matthewoliver/swift,hurricanerix/swift,openstack/swift,mjzmjz/swift,levythu/swift,Em-Pan/swift,bradleypj823/swift,levythu/swift,hbhdytf/mac2,takeshineshiro/swift,swiftstack/swift,hurricanerix/swift,redbo/swift,nadeemsyed/swift,psachin/swift,nadeemsyed/swift,smerritt/swift,mjwtom/swift,redhat-openstack/swift,wenhuizhang/swift,matthewoliver/swift,hbhdytf/mac,bouncestorage/swift,tipabu/swift,wenhuizhang/swift,Em-Pan/swift,clayg/swift,bkolli/swift,hbhdytf/mac2,williamthegrey/swift,bouncestorage/swift