Touch debug_fannie.log when installing CORE

just to prevent the warning

rattail_fabric2/corepos.py

@@ -104,6 +104,8 @@ def install_corepos(c, rootdir, rooturl_office, production=True,
     # fannie logging
     mkdir(c, '{}/fannie/logs'.format(is4c), use_sudo=True,
           owner='{}:www-data'.format(user), mode='0775')
+    c.sudo('touch {}/fannie/logs/debug_fannie.log'.format(is4c),
+           user='www-data')
 
 
 # TODO: deprecate / remove this