move btypes from headers to body of proton message

Fixes: https://pagure.io/koji/issue/3017

plugins/hub/protonmsg.py

@@ -210,13 +210,12 @@ def prep_build_state_change(cbtype, *args, **kws):
         old = koji.BUILD_STATES[old]
     new = koji.BUILD_STATES[kws['new']]
     address = 'build.' + new.lower()
-    btypeinfo = get_build_type(kws['info'])
     kws['info'] = _strip_extra(kws['info'])
+    kws['btypes'] = get_build_type(kws['info'])
     props = {'type': cbtype[4:],
              'name': kws['info']['name'],
              'version': kws['info']['version'],
              'release': kws['info']['release'],
-             'btypes': btypeinfo,
              'attribute': kws['attribute'],
              'old': old,
              'new': new}