printf debugging showed that the initial VSMW_New() call did not go
through vsm_vsmw_lock() / vsm_vsmw_unlock() simply because the
function pointers were not initialized yet.

This patch moves the init just after their initialization.

child_main() was previously called right after VSMW_New(), and
VSM_Init() is almost the first thing which child_main() calls, so
this move is mostly cosmetic.

Seen staring at #3948