[TEST] only reset clients on nightly tests
resetting the clients on each test (in after test) makes the tests running, especially in network mode, much slower, since transport client needs to be created each time when randmized to be used. Also, on OSX, the excessive connections causes bind exceptions eventually which makes running the network tests much harder on it.
closes #7329
[TEST] filter out keep alive timer thread name
Keep-Alive-Timer is an internal Java thread that might be started, make sure to filter it out
[STORE] Ignore segments.gen on metadata snapshots

The segments.gen file is optional and might even change while we
read it. It's safer to just ignore that file in the snapshot instead.
[STORE] Remove unnecessary deduplication
[STORE] Improve recovery / snapshot restoring file identity handling

This commit changes the way how files are selected for retransmission
on recovery / restore. Today this happens on a per-file basis where the
rather weak checksum and the file length in bytes is compared to check if
a file is identical. This is prone to fail in the case of a checksum collision
which can happen under certain circumstances.
The changes in this commit move the identity comparsion to a per-commit / per-segment
level where files are only treated as identical iff all the other files in the
commit / segment are the same. This "all or nothing" strategy is reducing the chance for
a collision dramatically since we also use a strong hash to identify commits / segments
based on the content of the ".si" / "segments.N" file.

Closes #7351