interrupt.exp: Revert back to checking gdb,noinferiorio at the top

The following patch will remove the gdb,noinferiorio setting from the
gdbserver boards, so this bit can be reverted.

gdb/testsuite/ChangeLog:
2015-07-29  Pedro Alves  <palves@redhat.com>

	* gdb.base/interrupt.exp: Revert back to checking gdb,noinferiorio
	at the top.

gdb/testsuite/ChangeLog

@@ -1,3 +1,8 @@
+2015-07-29  Pedro Alves  <palves@redhat.com>
+
+	* gdb.base/interrupt.exp: Revert back to checking gdb,noinferiorio
+	at the top.
+
 2015-07-29  Pedro Alves  <palves@redhat.com>
 
 	* gdb.base/call-ar-st.c: Include "../lib/unbuffer_output.c".

gdb/testsuite/gdb.base/interrupt.exp

@@ -18,6 +18,11 @@ if [target_info exists gdb,nointerrupts] {
     continue
 }
 
+if [target_info exists gdb,noinferiorio] {
+    verbose "Skipping interrupt.exp because of noinferiorio."
+    return
+}
+
 standard_testfile
 
 set options { debug }
@@ -45,11 +50,6 @@ if ![file exists $binfile] then {
     if [runto_main] then {
 	global inferior_spawn_id gdb_spawn_id
 
-	if {[target_info exists gdb,noinferiorio] && $inferior_spawn_id == $gdb_spawn_id} {
-	    verbose "Skipping interrupt.exp because of noinferiorio."
-	    return
-	}
-
 	set msg "process is alive"
 	gdb_test_multiple "continue" $msg {
 	    -i "$inferior_spawn_id" -re "talk to me baby\r\n" {