BUG/MEDIUM: cache: Don't cache objects if the size of headers is too big

HTTP responses with headers than impinge upon the reserve must not be
cached. Otherwise, there is no warranty to have enough space to add the header
"Age" when such cached responses are delivered.

This patch must be backported to 2.0 and 1.9. For these versions, the same must
be done for the legacy HTTP mode.

(cherry picked from commit b066747107bc27b6b94cec794cd76f12c5588795)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>

[Cf: The same was also done for the legacy HTTP mode]
1 file changed