LU-8136 tests: allow CT to registers with all MDTs

LU-8136 tests: allow CT to registers with all MDTs

With DNE, CT must register with all MDTs and thus need
additional time to do so.

Signed-off-by: Bruno Faccini <bruno.faccini@intel.com>
Change-Id: Id2342f6d2060649d08d423703173a70b3407ee8d
Reviewed-on: http://review.whamcloud.com/20258
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Sebastien Buisson <sebastien.buisson@bull.net>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>