Testsuite - Improve test1.68 to play nice with other running srun jobs

Run the srun job in the background initially to get pid.
Directly pass in the pid of the srun job instead of grabbing the first
srun pid found on the system.
Check that bg and fg actually succeed.

Bug 7022

testsuite/expect/test1.68

@@ -55,19 +55,27 @@ echo \"Test finished\"
 
 make_bash_script $stop_srun "
 $bin_sleep 15
-srun_proc=\$(ps -C srun -o pid=)
-echo \"sending job to the background, pid=\$srun_proc\"
+srun_proc=\$1
+echo \"suspending job, pid=\$srun_proc\"
 kill -s stop \$srun_proc
 "
 
 make_bash_script $test_srun "
 set -m
-./$stop_srun &
-$srun -v -t1 ./$test_timer
+$srun -v -t1 ./$test_timer &
+./$stop_srun \$! &
+wait
+echo \"sending job to the background\"
 bg
+if \[ \$? != 0 \]; then
+	echo \"BG Failed\"
+fi
 $bin_sleep 25
 echo \"sending job to foreground\"
 fg
+if \[ \$? != 0 \]; then
+	echo \"FG Failed\"
+fi
 "
 
 make_bash_script $file_in "
@@ -107,6 +115,16 @@ expect {
 		set fini_match 1
 		exp_continue
 	}
+	-re "BG Failed" {
+		send_user "\nFAILURE: Failed to find suspended srun job in background\n"
+		set exit_code 1
+		exp_continue
+	}
+	-re "FG Failed" {
+		send_user "\nFAILURE: Failed to find background srun job to put in foreground\n"
+		set exit_code 1
+		exp_continue
+	}
 	timeout {
 		send_user "\nFAILURE: srun is not responding\n"
 		set exit_code 1