As discussed with Albert, move the population of capabilities into the
identity package, making them static along the execution of the link.
When we receive the identityPackage, we collect the plugins we can use with
the device and stick to those. This should simplify the implementation and
remove the possibility to lose packages if packages are received before the
capabilities are processed in the former approach.
REVIEW: 128386
In case we need to discover the device (i.e. we're running the test in a
clean environment) we need to acquire the discovery mode.
Only initialize the test after setting the test mode enabled, so the
loopback is enabled.
