base: add basic tests

Currently in serverspec definition every profile has a -base role per
default. But there is no base_spec.rb file, so it actually runs
everything it finds for a given step. (step 1 == messaging_spec.rb
database_spec.rb etc...)
In more than 3 nodes deployments it actually fails.

Let's fix that by adding a basic test in testing 22 tcp (SSH) port.
Signed-off-by: Emilien Macchi <emilien.macchi@enovance.com>