[atomic] Add atomic_installer phase

This phase runs lorax with extra templates in Koji runroot task, links
the boot.iso to proper location in compose directory and adds the
installer iso to image manifest. This phase runs concurrently with live
media etc.

Signed-off-by: Lubomír Sedlář <lsedlar@redhat.com>

pungi/util.py

@@ -446,3 +446,12 @@ def find_old_compose(old_compose_dirs, release_short, release_version,
         return None
 
     return sorted(composes)[-1][1]
+
+
+def process_args(fmt, args):
+    """Given a list of arguments, format each value with the format string.
+
+    >>> process_args('--opt={}', ['foo', 'bar'])
+    ['--opt=foo', '--opt=bar']
+    """
+    return [fmt.format(val) for val in force_list(args or [])]