Fix test to handle output if allocation is delayed.

This primarily happens regularly if

PrologFlags=contain

Where the output has a nodename (and usually a number in it)

Normal output is

salloc: Granted job allocation 31159
1

but if the allocation is delayed you get output like

salloc: Granted job allocation 31161
salloc: Waiting for resource configuration
salloc: Nodes snowflake4 are ready for job
1
salloc: Relinquishing job allocation 31161

Where the test would key on the number in snowflake4 and fail.

This change makes it so the number has to be the first thing seen.

testsuite/expect/test15.39

@@ -86,7 +86,7 @@ expect {
 		set job_id $expect_out(1,string)
 		exp_continue
 	}
-	-re "($number)" {
+	-re "^($number)" {
 		set nodes $expect_out(1,string)
 		if {$nodes != 1} {
 			send_user "\nFAILURE: expected 1 allocated node\n"