[BUG] check for global.maxconn before doing accept()

[BUG] check for global.maxconn before doing accept()

If the accept() is done before checking for global.maxconn, we can
accept too many connections and encounter a lack of file descriptors
when trying to connect to the server. This is the cause of the
"cannot get a server socket" message  encountered in debug mode
during injections with low timeouts.
(cherry-picked from commit b00f9c456c0eadd26abbbf4bb0a3276da9f1844e)
(cherry picked from commit dea567ef66e1f0d6eafe29ff8a9c68b54ff40c90)