MINOR: checks: Simplify matching on HTTP headers in HTTP expect rules

MINOR: checks: Simplify matching on HTTP headers in HTTP expect rules

Extra parameters on http-check expect rules, for the header matching method, to
use log-format string or to match full header line have been removed. There is
now separate matching methods to match a full header line or to match each
comma-separated values. "http-check expect fhdr" must be used in the first case,
and "http-check expect hdr" in the second one. In addition, to match log-format
header name or value, "-lf" suffix must be added to "name" or "value"
keyword. For intance:

   http-check expect hdr name "set-cookie" value-lf -m beg "sessid=%[var(check.cookie)]"

Thanks to this changes, each parameter may only be interpreted in one way.