kdumpctl: skip selinux-relabel for dracut_args --mount dump target

When using "dracut_args --mount" to specify dump target, e.g. nfs like:
    path /
    core_collector makedumpfile -d 31
    dracut_args --mount "host:/path /var/crash nfs defaults"
kdump service should neither guarantees the correctness, nor relabels it.

For current code, since dracut_args dump targets are likely not mounted
so kdump service mistakenly relabel the rootfs, which is meanless and
takes very long time.

Signed-off-by: Pingfan Liu <piliu@redhat.com>

kdumpctl

@@ -946,6 +946,9 @@ path_to_be_relabeled()
 		fi
 	fi
 
+	if is_mount_in_dracut_args; then
+		return;
+	fi
 	_path=$(get_save_path)
 	# if $_path is masked by other mount, we will not relabel it.
 	_rmnt=$(df $_mnt/$_path 2>/dev/null | tail -1 | awk '{ print $NF }')