tests/taskmanager: protect against a messy git tree
tests/taskmanager: protect against a messy git tree

If a 'keyfile' file exists in this directory, the test breaks, and it's
tempting to go way back in git bisect trying to find out where the
breakage occurred.

Tarsnap/tarsnap-gui,Tarsnap/tarsnap-gui,Tarsnap/tarsnap-gui,Tarsnap/tarsnap-gui,Tarsnap/tarsnap-gui