periodic HIP fix: ping /ssl-vpn/hipreportcheck.esp at specified interval no matter...

periodic HIP fix: ping /ssl-vpn/hipreportcheck.esp at specified interval no matter what

This is a fix for the very subtle regression between v8.05 and v8.08 described in this thread: https://lists.infradead.org/pipermail/openconnect-devel/2020-April/005609.html

- Server never asks for HIP report submission, and no HIP script specified
  with `--csd-wrapper`
- v8.05 successfully rekeys 1 minute before server-specified rekey interval,
  and continues successfully
- v8.08 appears to successfully rekey, but then gets forced off one minute
  later
- Only apparent difference between the two is that v8.05 re-pings
  /ssl-vpn/hipreportcheck.esp every time it gets the config
  (/ssl-vpn/getconfig.esp), whereas v8.08 only pings it exactly once.

The bottom line is that _even if_ we have no mechanism to actually submit a
HIP report (no `--csd-wrapper`) and _even if_ we think the server will say
"no HIP report needed" every time we check, in order to keep the server from
kicking the client off, we should still…

* ping /ssl-vpn/hipreportcheck.esp at the interval (specified by the portal or `--force-trojan` or 1 hour default)
* ping /ssl-vpn/hipreportcheck.esp every time we re-fetch the config (/ssl-vpn/getconfig.esp) in order to rekey or reconnect

Signed-off-by: Daniel Lenski <dlenski@gmail.com>