This method is the locked bottom of onAuthComplete(), rename it and
split out onOpenComplete(), making the flow more linear. Also switch
to use getException() to discern success/failure, fixing up badly-named
mocks.
JIRA: NETCONF-905
Change-Id: I7a0c20b872b19b66e99144d0ce83636d6b4cd400 Signed-off-by: Robert Varga <robert.varga@pantheon.tech>