Several flags have in recent times been added to ajp_common.c, with
initialisation code in mod_jk:
- disable_reuse
- flush_headers
- flush_packets

These were not initialised in the IIS connector, and thus when they were
checked, uninitialised memory was being accessed, with the result that they were
all evaluated as being set.

This results in AJP13 connections between the connector and Tomcat not being
reused, and every header and packet write causing a flush. i.e. we're back in
the AJP12 days.

I've attached a patch to correct this, with an attempt at a check to ensure it
doesn't accidentally get broken again - I'd be open to other ways of achieving
this (e.g. documenting the jk_ws_service_t definition or a shared default
initialiser).