CLI to control backend health, rather than rely on probes.

Submitted by:	Federico G. Schwindt

clearer for everybody.

Add restart in vcl_miss{} implementation.

Note that we get into vcl_error{} on 413 and 417 also.

Rearrange the order in which we do things in cnt_start, to be more
consistent and correct: Process Connection: and Expect: headers
before we snapshot and possibly head into vcl_error{}.

We should never come in with a busyobj or obj.

Always allocate obj from Transient storage.

was related to the entry parameters of cnt_error(), but I belive it
has long been OBE, and now gets in the way of streaming.

cruft now not needed.

cache_session.c

two pointers in workers.

where it rightfully belongs.

Presently unused and untested.

Found by: Federico G. Schwindt <fgsch@lodoss.net>

Varnish sets SO_RCVTIMEO to cache_param->timeout_idle on the listen
sockets, so that the value is inherited to the accept()ed
connections. This has the side effect of making accept() returning
with EAGAIN after cache_param->timeout_idle seconds when there are no
connections coming in, and each of these timeouts is counted as a
sess_failed. Also the pacing sleep time is increased for each of these
timeouts, causing Varnish to react slowly at first when connections
start coming in.

Patch changes to loop around the call to accept() while EAGAIN

Without doing SES_Charge, the worker will panic at the end of
CNT_Session() when a request is aborted before it is complete.

Found by: Federico G. Schwindt <fgsch@lodoss.net>

Rename http_FilterHeader() to http_FilterReq()
Add http_FilterResp()
make http_FilterFields() static
remove http_CopyResp()

Eliminate the HTTPH_A_DELIVER filter which only took out "Date:"
because we always overwrite Date: anyway.

The attached patch is a one-liner for waiter/cache_waiter_ports.c,
the code was referencing sp->t_open where it should have been
sp->t_idle, which was causing assertion failures on idle session
timeouts.

POSIX threads don't have a thread identifier that can be printed
in a portable manner.