Use riptano/collectd to 0.1.6 (build on ubuntu 18.04)

[tlasica]

This new image version (0.1.6) tarball is build using ubuntu:18.04 instead of 16.04.

It is expected to be more secure in terms of the versions of the binary libraries included.

0.1.5 has disabled modbus module.

[tlasica]

@adejanovski I am trying to see if collectd 0.1.6 (built on ubuntu:18.04) works as expected. Unforuntately the collectd repo is not super reach in tests so I am using PR for this repo to run some tests (in addition to DSE ones).

I wonder if:

1. I can rerun the actions - does not seem to be allowed
2. see the collectd/cassandra logs from the test runs

[tlasica]

Apparently increasing timeout fixed the problem with failed test.