completion: fix branch.autosetup(merge|rebase)

When attempting to complete

  $ git config branch.auto<TAB>

'autosetupmerge' and 'autosetuprebase' don't come up. This is because
"$cur" is matched with "branch.*" and a list of branches are
completed. Add 'autosetup(merge|rebase)' to the list of branches using
__gitcomp_2 ().

Also take care to not complete

  $ git config branch.autosetupmerge.<TAB>
  $ git config branch.autosetuprebase.<TAB>

with the usual branch.<name>. candidates.

Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>
completion: fix remote.pushdefault

When attempting to complete

  $ git config remote.push<TAB>

'pushdefault' doesn't come up. This is because "$cur" is matched with
"remote.*" and a list of remotes are completed. Add 'pushdefault' to the
list of remotes using __gitcomp_2 ().

Also take care to not complete

  $ git config remote.pushdefault.<TAB>

with the usual remote.<name>. candidates.

Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>