staging/lustre/obdclass: be more careful processing server name

Because whole options line gets passed to exclude processing, don't
search from end of passed in argument to determine fsname at
beginning.

Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-2200
Lustre-change: http://review.whamcloud.com/6197


Signed-off-by: Nathaniel Clark <nathaniel.l.clark@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>
Signed-off-by: Peng Tao <tao.peng@emc.com>
Signed-off-by: Andreas Dilger <andreas.dilger@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>