staging: lustre: ptlrpc: Forbid too early NRS policy tunings

staging: lustre: ptlrpc: Forbid too early NRS policy tunings

Wait for a NRS policy to be fully started before allowing
to apply related tunings, so that all fields are properly
initialized.

Signed-off-by: Henri Doreau <henri.doreau@cea.fr>
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-6673
Reviewed-on: http://review.whamcloud.com/15104
Reviewed-by: Emoly Liu <emoly.liu@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: James Simmons <jsimmons@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>