extra-iso: Fix treeinfo

Remove boot.iso references and add [media] section.

JIRA: COMPOSE-2974
JIRA: COMPOSE-2975
Signed-off-by: Lubomír Sedlář <lsedlar@redhat.com>

tests/fixtures/extraiso-expected.treeinfo

@@ -1,6 +1,3 @@
-[checksums]
-images/boot.iso = sha256:fc8a4be604b6425746f12fa706116eb940f93358f036b8fbbe518b516cb6870c
-
 [general]
 ; WARNING.0 = This section provides compatibility with pre-productmd treeinfos.
 ; WARNING.1 = Read productmd documentation for details about new format.
@@ -20,12 +17,15 @@ type = productmd.treeinfo
 version = 1.2
 
 [images-x86_64]
-boot.iso = images/boot.iso
 
 [images-xen]
 initrd = images/pxeboot/initrd.img
 kernel = images/pxeboot/vmlinuz
 
+[media]
+discnum = 1
+totaldiscs = 1
+
 [release]
 name = Test
 short = T

tests/test_extra_isos_phase.py

@@ -630,13 +630,7 @@ class TweakTreeinfoTest(helpers.PungiTestCase):
         expected = os.path.join(helpers.FIXTURE_DIR, "extraiso-expected.treeinfo")
         extra_isos.tweak_treeinfo(compose, ["Client"], input, output)
 
-        with open(expected) as f:
-            expected = f.read()
-        with open(output) as f:
-            actual = f.read()
-
-        self.maxDiff = None
-        self.assertEqual(expected, actual)
+        self.assertFilesEqual(output, expected)
 
 
 if __name__ == '__main__':