LU-1415 tests: Handle OFD procfs changes

LU-1415 tests: Handle OFD procfs changes

This patch handles these procfs entry changes in OFD:

  - obdfilter.*.mntdev -> osd-*.*.mntdev
  - obdfilter.*.<cache_related> -> osd-*.*.<cache_related>

Change-Id: Ie9fac69446b5c183bc8eed44a86338ef62197529
Signed-off-by: Li Wei <liwei@whamcloud.com>
Reviewed-on: http://review.whamcloud.com/2934
Reviewed-by: Yu Jian <yujian@whamcloud.com>
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>