fix wait bug in init

BUGS

@@ -11,10 +11,6 @@ main.c:
 
 	cpus[0] -> cpus[bcpu]
 
-init.c:
-	should while(wait() >= 0);
-	not just wait();
-
 proc.c:
 	comment at top of scheduler() should say
 		via longjmp back to the scheduler

init.c

@@ -11,7 +11,7 @@ char *sh_args[] = { "sh", 0 };
 int
 main(void)
 {
-  int pid;
+  int pid, wpid;
 
   if(open("console", O_RDWR) < 0){
     mknod("console", T_DEV, 1, 1);
@@ -21,6 +21,7 @@ main(void)
   dup(0);  // stderr
 
   for(;;){
+    puts("init: starting sh\n");
     pid = fork();
     if(pid < 0){
       puts("init: fork failed\n");
@@ -30,8 +31,8 @@ main(void)
       exec("sh", sh_args);
       puts("init: exec sh failed\n");
       exit();
-    } else {
-      wait();
     }
+    while((wpid=wait()) >= 0 && wpid != pid)
+      ;
   }
 }