Bug 2976: squid reports ERR_INVALID_URL for transparently captured requests when...

Bug 2976: squid reports ERR_INVALID_URL for transparently captured requests when reconfiguring

During reconfigure the configured AnyP::PortCfg objects in http_port_list
may deleted so it is not safe to use them while processing Http requests.
For this reason inside prepareTransparentURL (file client_side.cc) function
the protocol was hard-coded to "http" instead of read it from the related
AnyP::PortCfg object.
But this is breaks the intercepted https traffic.

This patch:
  1. Inside prepareTransparentURL read the protocol from the related
     AnyP::PortCfg object
  2. add_http_port() locks the new port pointer before linking it.
  3. parsePortCfg() locks the new port pointer before linking it.
  4. free_PortCfg() unlock the old port pointer before unlinking
     it. It does not delete the old pointer.

This patch also discussed in squid-dev user mailing list in
 "Re: [PATCH] Squid host rewrite for intercepted https requests"
thread.

This is a Measurement Factory project