Add probetest for response with duplicate frags
Add probetest for response with duplicate frags

When an SSYNC connection fails after shipping a fragment, but before
cleaning itself up - it can lead to multiple replicas of the same
fragment index serviceable in the node_iter at the same time.  Or
perhaps more likely if a partner nodes win a race to rebuild waiting
on a handoff.  In this case, the proxy need not fail to service a GET
just because of extra information.  A similar guard was added to the
reconstructor in a related change [1].

This underlying bug is acctually fixed by the related change [2], this
probetest is just encoding the failure to help with future maintenance.

1. Related-Change: I91f3d4af52cbc66c9f7ce00726f247b5462e66f9
2. Related-Change: I2310981fd1c4622ff5d1a739cbcc59637ffe3fc3

Closes-Bug: 1624176

Change-Id: I06fc381a25613585dd18916d50e7ca2c68d406b6

swiftstack/swift,notmyname/swift,hurricanerix/swift,nadeemsyed/swift,clayg/swift,matthewoliver/swift,psachin/swift,smerritt/swift,openstack/swift,nadeemsyed/swift,psachin/swift,matthewoliver/swift,smerritt/swift,clayg/swift,swiftstack/swift,matthewoliver/swift,notmyname/swift,clayg/swift,notmyname/swift,hurricanerix/swift,smerritt/swift,psachin/swift,notmyname/swift,nadeemsyed/swift,tipabu/swift,psachin/swift,tipabu/swift,hurricanerix/swift,nadeemsyed/swift,tipabu/swift,swiftstack/swift,openstack/swift,smerritt/swift,redbo/swift,matthewoliver/swift,redbo/swift,openstack/swift,clayg/swift,hurricanerix/swift,tipabu/swift,openstack/swift