Modify test and srun immediate error message slightly

The srun message changed for pack jobs and the test failed.
  Tweak both message and test for better clarity.

src/srun/libsrun/launch.c

@@ -350,7 +350,7 @@ extern int launch_common_create_job_step(srun_job_t *job, bool use_all_cpus,
 		     (rc != SLURM_PROTOCOL_SOCKET_IMPL_TIMEOUT) &&
 		     (rc != ESLURM_INTERCONNECT_BUSY) &&
 		     (rc != ESLURM_DISABLED))) {
-			error("Unable to create job %u step: %m",
+			error("Unable to create step for job %u: %m",
 			      job->ctx_params.job_id);
 			return SLURM_ERROR;
 		}

testsuite/expect/test1.14

@@ -220,7 +220,7 @@ expect {
 		set exit_code 1
 		exp_continue
 	}
-	-re "Unable to create job step" {
+	-re "Unable to create " {
 		send_user "This error was expected, no worries\n"
 		incr matches
 		exp_continue