[doctor] fix node-label setting

Current doctor verify jobs need to be run on relevant pods which are
specified by slave-label. But, after multijob introduced, the parameter
is not passed to children jobs. Also, 'phase' of project is misleading,
as it isn't multijob's phase.

This patch makes sure each doctor job run on correct pod by updating
node label rule for doctor pod to 'doctor-{installer}-{arch}'.

This patch also merges doctor slave parameter definitions into one,
and deletes unnecessary setting where default are set.

Change-Id: Ic9bf218ae7fb4f9866b510efd1e0ccd19277b78e
Signed-off-by: Ryota MIBU <r-mibu@cq.jp.nec.com>