Fix an inconsistency in ::arakoon::buffer::reset().

The buffer should be set to 'None' also if it does not have ownership of the data.
Merge pull request #13 from bas-at-amplidata/buffer_reset_fix

Fix an inconsistency in ::arakoon::buffer::reset().
TravisCI: Use AMD64 packages

Change-Id: I3c8b01e58c4da6c9718b45c4c272b2bfaf4291e6