coroutine: trim down nesting level in perf_nesting test

20000 nested coroutines require 20 GB of virtual address space.
Only nest 1000 of them so that the test (only enabled with
"-m perf" on the command line) runs on 32-bit machines too.

Cc: qemu-stable@nongnu.org
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
Reviewed-by: NStefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

tests/test-coroutine.c

@@ -183,7 +183,7 @@ static void perf_nesting(void)
     double duration;
 
     maxcycles = 100000000;
-    maxnesting = 20000;
+    maxnesting = 1000;
     Coroutine *root;
     NestData nd = {
         .n_enter  = 0,