[PATCH] detaching sslbump from accel mode

So, in theory ssl-bump is a form of intercept not a form of
accelerator. Its use of prepareAcceleratorURL() to convert the partial
to absolute URL unconditionally sets the accel flag with a mix of side
effects. Some bad ones have been identified already.

This patch changes the flag setting, to allow ssl-bump to use the URL
preparation function without the side effects. I'm in half a mind to
make a ssl-bump specific URL preparation function, but only after this
is proven workable.

Christos: as the person who appears to have the best testing ability for
ssl-bump can you run your tests over the resulting Squid and check that
the expected behaviours have not changed for the worse? I am fully
expecting there to be several as yet unknown places needing to add a
test of the sslBumped flag alongside testing accel flag.

I'm expecting this to fix the need for ssl-bump to configure
"always_direct allow" and for this to be the proper long-term fix for
the bug 2519 status mixup in comment 52 (comment 53 has an adequate
workaround for the bug patch while this gets tested).

Amos