LU-13116 mgc: do not lose sptlrpc config lock

LU-13116 mgc: do not lose sptlrpc config lock

Multiple targets on the same node can make use of the same lock on
sptlrpc config log. So if a target is being stopped, sptlrpc
config log should not be directly marked as stopping.

Fixes: 0ad54d5977 ("LU-11185 mgc: config lock leak")
Signed-off-by: Sebastien Buisson <sbuisson@ddn.com>
Change-Id: I09c2b0c276daadb66721df88c33f734ebba86114
Reviewed-on: https://review.whamcloud.com/37344
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Alexander Boyko <c17825@cray.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>