BUG/MINOR: http-ana: Don't increment conn_retries counter before the L7 retry

BUG/MINOR: http-ana: Don't increment conn_retries counter before the L7 retry

When we are about to perform a L7 retry, we deal with the conn_retries
counter, to be sure we can retry. However, there is an issue here because
the counter is incremented before it is checked against the backend
limit. So, we can miss a connection retry.

Of course, we must invert both operation. The conn_retries counter must be
incremented after the check agains the backend limit.

This patch must be backported as far as 2.6.