BUG/MEDIUM: mworker: use default maxconn in wait mode

BUG/MEDIUM: mworker: use default maxconn in wait mode

In bug #1751, it was reported that haproxy is consumming too much memory
since the 2.4 version. This is because of a change in the master, which
loses completely its configuration in wait mode, and lose its maxconn.

Without the maxconn, haproxy will try to compute one itself, and will
allocate RAM consequently, too much in our case. Which means the master
will have a too high maxconn and too much RAM allocated.

The patch fixes the issue by setting the maxconn to the default value
when re-executing the master in wait mode.

Must be backported as far as 2.5.