Report libpq errors correctly if session setup or teardown steps fail in

isolation regression tests.

Alvaro committed these fixes to master branch on Tue Jul 29th, as part of
Noah Misch's patch. The rest of that patch is not needed on 9.1, but this
part should be backpatched.

src/test/isolation/isolationtester.c

@@ -286,7 +286,7 @@ run_permutation(TestSpec * testspec, int nsteps, Step ** steps)
 			{
 				fprintf(stderr, "setup of session %s failed: %s",
 						testspec->sessions[i]->name,
-						PQerrorMessage(conns[0]));
+						PQerrorMessage(conns[i]));
 				exit_nicely();
 			}
 			PQclear(res);
@@ -333,7 +333,7 @@ run_permutation(TestSpec * testspec, int nsteps, Step ** steps)
 			{
 				fprintf(stderr, "teardown of session %s failed: %s",
 						testspec->sessions[i]->name,
-						PQerrorMessage(conns[0]));
+						PQerrorMessage(conns[i]));
 				/* don't exit on teardown failure */
 			}
 			PQclear(res);