LU-15059 nrs: do not overwrite "cmd" in nrs_tbf_rule

LU-15059 nrs: do not overwrite "cmd" in nrs_tbf_rule

"cmd" pointer inside ptlrpc_lprocfs_nrs_tbf_rule_seq_write() and
nrs_tbf_parse_cmd are static. This could cause a double kfree call
because "cmd" could be overwriten by another "nrs_tbf_rule" write
instance.

Let's try to remove the "static" definition.

Signed-off-by: Etienne AUJAMES <eaujames@ddn.com>
Change-Id: I8cd7d9dd0483778c82bbf8711c07e49255983f4b
Reviewed-on: https://review.whamcloud.com/45142
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Li Xi <lixi@ddn.com>