bhyve: init checkput before caph_enter

init_checkpoint_thread binds to a socket. Bhyve isn't allowed to do that
after caph_enter.

Reviewed by: corvink, markj
MFC after: 1 week
Sponsored by: vStack
Differential Revision: https://reviews.freebsd.org/D38857

(cherry picked from commit 9a9a248964696f45260ea026aa5f9174cc86b137)