pNFS: Fix RCU lock leakage

Another brown paper bag moment. pnfs_alloc_ds_commits_list() is leaking
the RCU lock.

Fixes: a9901899b649 ("pNFS: Add infrastructure for cleaning up per-layout commit structures")
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
diff --git a/fs/nfs/pnfs_nfs.c b/fs/nfs/pnfs_nfs.c
index 25f1355..e7ddbce 100644
--- a/fs/nfs/pnfs_nfs.c
+++ b/fs/nfs/pnfs_nfs.c
@@ -501,6 +501,7 @@
 		rcu_read_lock();
 		pnfs_put_commit_array(array, cinfo->inode);
 	}
+	rcu_read_unlock();
 	return ret;
 }