Sending a Cookie header with a webvpncontext= value whose base64-decoded
length exceeds SID_SIZE crashes the worker with SIGSEGV before it can
send an HTTP response. The test detects both pre- and post-response
crashes: a connection reset (HTTP 000) and a "died with sigsegv" entry
in the server log respectively.
Relates: #719
Signed-off-by: Nikos Mavrogiannopoulos <n.mavrogiannopoulos@gmail.com>