Introduce a workaround for join aliases
Introduce a workaround for join aliases

When there is a join alias, var->varnosync will point to the alias and
var->varno will point to the table itself, but we need to use the alias
when deparsing the query. Hence a workaround is introduced to solve this
problem in ruleutils. Normally this case can be understood with
dpns->plan == NULL check but in our case, dpns->plan is always NULL. We
should sync our ruleutils at some point with postgres ruleutils. This
could be a wrong solution as well but the tests pass.

citusdata/citus,citusdata/citus,citusdata/citus,citusdata/citus,citusdata/citus