BUG/MEDIUM: connection: Wake the stconn on error when failing to create mux

BUG/MEDIUM: connection: Wake the stconn on error when failing to create mux

When the app_ops were removed, direct calls to the SC wake callback function
were replaced by tasklet wakeups. However, in conn_create_mux(), it was
replaced by a direct call to sc_conn_process(). However, sc_conn_process()
is only usable when the SC is attach to a stream. A backend mux can be
created for a healcheck. In this context, sc_conn_process() cannot be
called.

Because of this bug, crashes can be experienced when an error is triggered
during a SSL connection attempt from a healthcheck.

To fix the issue, the call to sc_conn_process() was replaced by a tasklet
wakeup.

This patch should fix the issue #3326. No backport needed.