Fix the issue that a GTM Proxy sends error responses via unrelated connection again.
Remove some redundancy from GTM proxy.
Fix the issue about renumbering a connection id in GTM proxy.
When a backend disconnect from a GTM proxy, the proxy renumbers a connection id of the connection located in last slot of a connection array. GTM proxy doesn't notify
that action to a GTM. Then a GTM could release unrelated transaction ids.
Collection of queries used with -k option.   With -k option, all the tables
are distributed with bid and queries should have used correct bid value.  The
commit correct this.

Submitted by Tetsuo Sakata.