BUG/MEDIUM: mworker: don't call the thread and fdtab deinit

BUG/MEDIUM: mworker: don't call the thread and fdtab deinit

Before switching to wait mode, the per thread deinit should not be
called, because we didn't initiate threads and fdtab.

The problem is that the master could crash if we try to reload HAProxy

The commit 944e619 ("MEDIUM: mworker: wait mode use standard init code
path") removed the deinit code by accident, but its fix 7c756a8
("BUG/MEDIUM: mworker: fix FD leak upon reload") was incomplete and did
not took care of the WAIT_MODE.

This fix must be backported in 1.9 and 2.0