BUG/MINOR: http-ana/filters: Wait end of the http_end callback for all filters

BUG/MINOR: http-ana/filters: Wait end of the http_end callback for all filters

Filters may define the "http_end" callback, called at the end of the analysis of
any HTTP messages. It is called at the end of the payload forwarding and it can
interrupt the stream processing. So we must be sure to not remove the XFER_BODY
analyzers while there is still at least filter in progress on this callback.

Unfortunatly, once the request and the response are borh in the DONE or the
TUNNEL mode, we consider the XFER_BODY analyzer has finished its processing on
both sides. So it is possible to prematurely interrupt the execution of the
filters "http_end" callback.

To fix this bug, we switch a message in the ENDING state. It is then switched in
DONE/TUNNEL mode only after the execution of the filters "http_end" callback.

This patch must be backported (and adapted) to 2.1, 2.0 and 1.9. The legacy HTTP
mode shoud probaly be fixed too.