Run the migration command directly in the if-statement

Since there is set -e set, it would fail too early even if the container
worked as expected.

Author: hhorak

test/run_migration_test

@@ -56,8 +56,7 @@ assert_migration_succeeds ()
 # test case suggested in https://github.com/sclorg/postgresql-container/pull/521
 assert_migration_fails()
 {
-    docker run --rm -e POSTGRESQL_MIGRATION_REMOTE_HOST=invalid-host-name -e POSTGRESQL_MIGRATION_ADMIN_PASSWORD=password "$image_to" run-postgresql --version
-    if [ $? -eq 0 ] ; then
+    if docker run --rm -e POSTGRESQL_MIGRATION_REMOTE_HOST=invalid-host-name -e POSTGRESQL_MIGRATION_ADMIN_PASSWORD=password "$image_to" run-postgresql --version ; then
       info "The image exited with 0 despite migration obviously did not work, that's a problem."
       return 1
     else