Pull out stat thread launches

According to Jim Lieb they don't even compile.

Signed-off-by: Adam C. Emerson <aemerson@linuxbox.com>
Swallow up state async request thread

This is not tested beyond making sure it comes up and shuts down.  I
do not yet have an FSAL that supports asynchronous blocking locks, so
someone with one will need to go over this.

Signed-off-by: Adam C. Emerson <aemerson@linuxbox.com>