Mimic GET reforwarding decisions when our CONNECT fails (#1168)

Mimic GET reforwarding decisions when our CONNECT fails (#1168)

Use FwdState::reforwardableStatus() logic when deciding whether to
reforward our CONNECT request after a failed tunneling attempt.

Also honor forward_max_tries limit when retrying tunneling attempts.

These TunnelStateData fixes deal with ordinary CONNECT traffic (no
SslBump). FwdState also handles CONNECT requests (with SslBump). We make
that CONNECT handling more consistent across these classes (in addition
to making it more consistent across CONNECT and GET/etc. methods).

Co-authored-by: Alex Rousskov <rousskov@measurement-factory.com>