remove more six compatibility layer

[a-detiste]

Hi, I continue working on this in small steps.

pyflakes3 linter is giving me scary warnings.

./pywebdav/lib/davcopy.py:98:17: undefined name 'ms' seems to be a good catch.

tchet@quieter:~/git/PyWebDAV3$ pyflakes3 .  | grep undef
./pywebdav/lib/iface.py:232:16: undefined name 'moveone'
./pywebdav/lib/iface.py:236:16: undefined name 'movetree'
./pywebdav/lib/iface.py:242:16: undefined name 'copyone'
./pywebdav/lib/iface.py:246:16: undefined name 'copytree'
./pywebdav/lib/davcopy.py:98:17: undefined name 'ms'
./pywebdav/server/mysqlauth.py:33:12: undefined name 'Mconn'
./pywebdav/server/fshandler.py:42:13: undefined name 'time'
./pywebdav/server/fshandler.py:53:25: undefined name 'dav_interface'