qemu-iotests: replace FSF postal addresses with www.gnu.org links

Blue Swirl notices that we were using the old FSF post address in the
license boilerplates.  Replace both the old and new address with links
to the gnu.org licenses homepage as suggested by Ben Pfaff.

Signed-off-by: Christoph Hellwig <hch@lst.de>
diff --git a/tests/qemu-iotests/019 b/tests/qemu-iotests/019
index 3f858dc..0c84d2f 100755
--- a/tests/qemu-iotests/019
+++ b/tests/qemu-iotests/019
@@ -17,9 +17,7 @@
 # GNU General Public License for more details.
 #
 # You should have received a copy of the GNU General Public License
-# along with this program; if not, write to the Free Software
-# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307
-# USA
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #
 
 # creator