EX-4963 lipe: rescan after registering a new changelog user

EX-4963 lipe: rescan after registering a new changelog user

In lamigo, if we register a new changelog user then force a rescan of
the device. Add hot-pools test_6c() to verify. Adjust hot-pools to be
more precise about param matching.

Test-Parameters: trivial testlist=hot-pools
Test-Parameters: trivial testlist=hot-pools env=ONLY=6c,ONLY_REPEAT=20
Signed-off-by: John L. Hammond <jhammond@whamcloud.com>
Change-Id: I9576d50f87ffe0eb5e44c62087fca317ddce50c7
Reviewed-on: https://review.whamcloud.com/46781
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Alex Zhuravlev <bzzz@whamcloud.com>
Reviewed-by: Alexandre Ioffe <aioffe@ddn.com>