Refactor lock_container into lock_config_[xx]

Refactor lock_container into lock_config_[xx]

This mimics the "signatures" of the methods in
QemuServer.pm, and should allow us to use this methods in a
future abstract "Guest" class.

It also changes the various timeouts (ranging from 1, 10, 60
to undef) to use the default timeout defined in the
lock_config methods (10).

Also drop the now unused use statement for flock.