--quiet does not suppress update status when branch has sub-trees

When dealing with a branch that has an external sub-tree, the --quiet option only suppresses one of the multiple update status messages.

Example of what a non-quiet update prints:
user@host:~/bzr/foo$ bzr update
External update src/bar
Tree is up to date at revision 65 of branch bzr+ssh://server/var/bzr/bar/bar
Tree is up to date at revision 65 of branch bzr+ssh://server/var/bzr/foo/foo
user@host:~/bzr/foo$

Example of what a quiet update prints:
user@host:~/bzr/foo$ bzr update --quiet
Tree is up to date at revision 65 of branch bzr+ssh://server/var/bzr/foo/foo
user@host:~/bzr/foo$

Expected behavior:
user@host:~/bzr/foo$ bzr update --quiet
user@host:~/bzr/foo$