Fix tx status tracking

[reshke]

psql (15beta1 (Ubuntu 15~beta1-1.pgdg20.04+1), server 15.4)
Type "help" for help.

db1=# commit;
WARNING:  client 0xc0003a81c0: error there is no transaction in progress
COMMIT
db1=# commit;
WARNING:  client 0xc0003a81c0: error there is no transaction in progress
COMMIT
db1=# commit;
WARNING:  client 0xc0003a81c0: error there is no transaction in progress
COMMIT
db1=# begin;
BEGIN
db1=*# commit;
ERROR:  client proccessing error: client relay has no connection to shards, tx status ACTIVE
db1=# begin;
BEGIN
db1=*# begin;
WARNING:  client 0xc0003a81c0: error there is already transaction in progress
BEGIN
db1=*# begin;
WARNING:  client 0xc0003a81c0: error there is already transaction in progress
BEGIN
db1=*# rollback ;
ERROR:  client proccessing error: ddl is forbidden inside multi-shard transition, tx status ACTIVE
db1=# rollback ;
WARNING:  client 0xc0003a81c0: error there is no transaction in progress
ROLLBACK
db1=# rollback ;
WARNING:  client 0xc0003a81c0: error there is no transaction in progress
ROLLBACK
db1=# rollback ;
WARNING:  client 0xc0003a81c0: error there is no transaction in progress
ROLLBACK
db1=# ^C
db1=# \q

[Denchick]

LGTM