Handle one TBPxelinuxConfig case where we should not mess with the config.

db/libdb.pm.in

@@ -584,6 +584,13 @@ sub TBPxelinuxConfig($;$)
 		}
 	    } elsif (defined($part)) {
 		$action = "diskboot";
+	    } elsif (!$actionp && $field eq "def_boot_osid") {
+		#
+		# We are probably calling from OSSelect after changing
+		# def_boot_osid but before loading the disk with that image.
+		# Just leave it alone.
+		#
+		return;
 	    } else {
 		print("*** Warning: invalid $field info for $nodeid, ".
 		      "booting to MFS\n");

db/nalloc.in

@@ -291,8 +291,9 @@ if (!$error && (!$noalloc || $partial) && @nodes) {
     # And since the node is now allocated, we need to redo its pxelinux
     # config file so it won't be stuck in pxewait
     foreach my $node (@need_pxeconfig) {
-	TBPxelinuxConfig($node)
-	    if ($node->boot_method() eq "pxelinux");
+	if ($node->boot_method() eq "pxelinux") {
+	    TBPxelinuxConfig($node);
+	}
     }
 }
 TBDebugTimeStamp("updated node_activity, history, and bootlogs");