Bump (again) the amount of work we do for wmem's timing test

Apparently the new win8 vm has a *very* low-resolution timer, and the allocators
are indistinguishable at the previous amount of work.

Change-Id: If4e5bb8f85b1f0d39658f54001c88f42ffddfc47
Reviewed-on: https://code.wireshark.org/review/2768
Reviewed-by: Evan Huus <eapache@gmail.com>

epan/wmem/wmem_test.c

@@ -353,7 +353,7 @@ wmem_time_allocator(wmem_allocator_type_t type)
 
     allocator = wmem_allocator_force_new(type);
 
-    for (j=0; j<1024; j++) {
+    for (j=0; j<2048; j++) {
         for (i=0; i<MAX_SIMULTANEOUS_ALLOCS; i++) {
             wmem_alloc(allocator, 8);
         }