LU-4981 tests: remount FS after writes to /proc

We should remount FS after writes all proc entry in 133g,
because some upcall value under /proc will be assigned to
some gabarge value, which will cause failures in the
following test.

Signed-off-by: wang di <di.wang@intel.com>
Change-Id: Ic120e19651a4a7897a6329a93feff1644c778286
Reviewed-on: http://review.whamcloud.com/10174
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>