system: Disable footholds while the package lock is held.
system: Disable footholds while the package lock is held.

This prevents prevents the package functions from being interrupted
at an inopportune time. This was causing Swank to lock up if C-c C-c
interrupted a thread the wrong moment.

Footholds are reenabled along the error path.

froggey/Mezzano,froggey/Mezzano