magit-refresh-buffer-1: favor parent over its siblings

Previously we unintentionally favored siblings of the
parent over the parent itself.
magit-process-buffer: remove unused CREATE argument

This argument is no longer respected this function
now always create the buffer if it doesn't exist yet.
magit-mode-refresh-buffer: don't fiddle with window point

See #1451.
magit-process-buffer: adjust the callers too
Merge branch 'master' into next

Conflicts:
	magit.el

Only code that no longer exists on 'next' was modified.