lockdown: remove unnecessary check for pair record file during pairing
lockdown: remove unnecessary check for pair record file during pairing

During device pairing the code in lockdownd_do_pair() is checking if there
is a pair record on disk for the current device, and then requests it from
usbmuxd. This additional check is not only unnecessary since usbmuxd can
obviously only return a pair record if it exists, but is also causing issues
on newer versions of macOS where /var/db/lockdown is mode 700.

Tatsh/libimobiledevice,Tatsh/libimobiledevice,libimobiledevice/libimobiledevice,libimobiledevice-win32/libimobiledevice,libimobiledevice-win32/libimobiledevice,libimobiledevice-win32/libimobiledevice,libimobiledevice-win32/libimobiledevice,libimobiledevice/libimobiledevice,Tatsh/libimobiledevice,Tatsh/libimobiledevice