REGTESTS: http-rules: test the tarpit, deny and silent-drop actions

REGTESTS: http-rules: test the tarpit, deny and silent-drop actions

The tarpit action was only referenced by the "set-timeout" test,
silent-drop was not covered at all, and deny was always used in its
default form, never with a customized status, body, content type or
extra header.

The test checks the default and the customized status of tarpit, the
"PT" termination state it produces in the log, the customized response
of deny, and that silent-drop closes the connection since we're using
rst-ttl here for portability reasons. The pause action is exercised
too, with a short delay.

"timeout tarpit" is set to a small value so that the test stays fast.