sql: fix ShowCreateTable test flakiness
sql: fix ShowCreateTable test flakiness

Need to use different names per create/drop to prevent
lease problems.

Fixes #6226

cockroachdb/cockroach,glycerine/cockroach,maxlang/cockroach,vaibhavarora/cockroach,petermattis/cockroach,paperstreet/cockroach,petermattis/cockroach,arjun4084346/cockroach,arjun4084346/cockroach,cockroachdb/cockroach,veteranlu/cockroach,vivekmenezes/cockroach,veteranlu/cockroach,sunya123/cockroach,vaibhavarora/cockroach,sunya123/cockroach,paperstreet/cockroach,arjun4084346/cockroach,sunya123/cockroach,vaibhavarora/cockroach,veteranlu/cockroach,maxlang/cockroach,paperstreet/cockroach,sunya123/cockroach,sunya123/cockroach,veteranlu/cockroach,vivekmenezes/cockroach,glycerine/cockroach,veteranlu/cockroach,arjun4084346/cockroach,vivekmenezes/cockroach,maxlang/cockroach,glycerine/cockroach,vivekmenezes/cockroach,petermattis/cockroach,veteranlu/cockroach,vivekmenezes/cockroach,cockroachdb/cockroach,paperstreet/cockroach,petermattis/cockroach,paperstreet/cockroach,vaibhavarora/cockroach,vaibhavarora/cockroach,glycerine/cockroach,vivekmenezes/cockroach,maxlang/cockroach,petermattis/cockroach,sunya123/cockroach,glycerine/cockroach,maxlang/cockroach,arjun4084346/cockroach,paperstreet/cockroach,sunya123/cockroach,maxlang/cockroach,vivekmenezes/cockroach,petermattis/cockroach,veteranlu/cockroach,maxlang/cockroach,petermattis/cockroach,glycerine/cockroach,sunya123/cockroach,petermattis/cockroach,vaibhavarora/cockroach,glycerine/cockroach,cockroachdb/cockroach,vivekmenezes/cockroach,cockroachdb/cockroach,arjun4084346/cockroach,cockroachdb/cockroach,veteranlu/cockroach,arjun4084346/cockroach,paperstreet/cockroach,cockroachdb/cockroach,maxlang/cockroach,arjun4084346/cockroach,glycerine/cockroach,cockroachdb/cockroach,paperstreet/cockroach,vaibhavarora/cockroach,vaibhavarora/cockroach