use serialize_profile() for the new profile in (V)iew Changes

... instead of serialize_profile_from_old_profile()

This will give a realistic preview of the changes (serialize_profile()
is also used when actually writing the profile) and replaces the
known-buggy serialize_profile_from_old_profile() with known-working
code.

It also fixes the issue reported in
    https://bugs.launchpad.net/ubuntu/+source/apparmor/+bug/1528139
which means we no longer need the workaround of catching AttributeError
(verified in manual before/after test)

References:
- https://bugs.launchpad.net/apparmor/+bug/1394788
- https://bugs.launchpad.net/bugs/1528139
- https://bugs.launchpad.net/apparmor/+bug/1404893

(cherry picked from commit 469eb444de)

utils/apparmor/aa.py

@@ -1869,11 +1869,9 @@ def save_profiles():
                 else:
                     oldprofile = get_profile_filename(which)
 
-                try:
-                    newprofile = serialize_profile_from_old_profile(aa[which], which, '')
-                except AttributeError:
-                    # see https://bugs.launchpad.net/ubuntu/+source/apparmor/+bug/1528139
-                    newprofile = "###\n###\n### Internal error while generating diff, please use '%s' instead\n###\n###\n" % _('View Changes b/w (C)lean profiles')
+                serialize_options = {}
+                serialize_options['METADATA'] = True
+                newprofile = serialize_profile(aa[which], which, serialize_options)
 
                 aaui.UI_Changes(oldprofile, newprofile, comments=True)