BUG/MAJOR: dns: dns client resolution infinite loop

BUG/MAJOR: dns: dns client resolution infinite loop

Under certain circonstance (a configuration with many servers relying on
DNS resolution and one of them triggering the replay of a request
because of a timeout or invalid response to an ANY query), HAProxy could
end up in an infinite loop over the currently supposed running DNS
queries.

This was caused because the FIFO list of running queries was improperly
updated in snr_resolution_error_cb. The head of the list was removed
instead of the resolution in error, when moving the resolution to the
end of the list.

In the mean time, a LIST_DEL statement is removed since useless. This
action is already performed by the dns_reset_resolution function.