Use HW_PHYSMEM instead of HW_USERMEM in get_total_system_memory_impl

The code checked for sysctl being available and HW_PHYSMEM being
defined, but HW_USERMEM was actually being used with sysctl instead
of HW_PHYSMEM.

The case for OpenBSD, etc. use HW_PHYSMEM64 (which is obviously a
64-bit variant of HW_PHYSMEM) and the case for OSX uses HW_MEMSIZE
(which appears to be a 64-bit variant of HW_PHYSMEM).

Signed-off-by: Kris Katterjohn <katterjohn@gmail.com>

src/lib/meminfo/meminfo.c

@@ -130,7 +130,7 @@ get_total_system_memory_impl(void)
    * HW_PHYSMEM. */
   size_t memsize=0;
   size_t len = sizeof(memsize);
-  int mib[2] = {CTL_HW, HW_USERMEM};
+  int mib[2] = {CTL_HW, HW_PHYSMEM};
   if (sysctl(mib,2,&memsize,&len,NULL,0))
     return 0;