Fix incorrect default_groups when parsing projects from XML manifest

Change Details:
* Switch first default group to 'all' instead of 'default'

Change Benefits:
* More consistent with default_groups in the counterpart Save() function
* Fixes bug where command 'repo manifest' added an extra 'default'
  group to every output project element groups attribute. This bug was
  particularly confusing for projects which had 'groups="notdefault"'
  as they were output as 'groups="notdefault,default"' by 'repo manifest'

Change-Id: I5611c027a982d3394899466248b971910bec8c6b
1 file changed