BUG/MEDIUM: dns: Properly initialize new DNS session

When a new DNS session is created, all its fields are not properly
initialized. For instance, "tx_msg_offset" can have any value after the
allocation. So, to fix the bug, pool_zalloc() is now used to allocate new
DNS session.

This patch should fix the issue #1781. It must be backported as far as 2.4.
1 file changed