cli: Avoid os.Exit in `sql -e`
cli: Avoid os.Exit in `sql -e`

Discovered while writing a test which would have to run a failing
invocation, which before this change would simply quit the process.

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