iotests: Move _filter_nbd into common.filter

_filter_nbd can be useful for other NBD tests, too, therefore it should
reside in common.filter.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

tests/qemu-iotests/083

@@ -49,18 +49,6 @@ wait_for_tcp_port() {
 	done
 }
 
-_filter_nbd()
-{
-    # nbd.c error messages contain function names and line numbers that are
-    # prone to change.  Message ordering depends on timing between send and
-    # receive callbacks sometimes, making them unreliable.
-    #
-    # Filter out the TCP port number since this changes between runs.
-    sed -e 's#^.*nbd/.*\.c:.*##g' \
-        -e 's#nbd:127\.0\.0\.1:[^:]*:#nbd:127\.0\.0\.1:PORT:#g' \
-        -e 's#\(exportname=foo\|PORT\): Failed to .*$#\1#'
-}
-
 check_disconnect() {
 	event=$1
 	when=$2

tests/qemu-iotests/common.filter

@@ -230,5 +230,17 @@ _filter_qemu_img_map()
         -e 's/Mapped to *//' | _filter_testdir | _filter_imgfmt
 }
 
+_filter_nbd()
+{
+    # nbd.c error messages contain function names and line numbers that are
+    # prone to change.  Message ordering depends on timing between send and
+    # receive callbacks sometimes, making them unreliable.
+    #
+    # Filter out the TCP port number since this changes between runs.
+    sed -e 's#^.*nbd/.*\.c:.*##g' \
+        -e 's#nbd:127\.0\.0\.1:[^:]*:#nbd:127\.0\.0\.1:PORT:#g' \
+        -e 's#\(exportname=foo\|PORT\): Failed to .*$#\1#'
+}
+
 # make sure this script returns success
 true