Add missing dependencies to tools/init/test-requirements.txt
for running unit tests. Libraries are placed in test-
requirementss.txt rather than requirements.txt due to library
versions included within the snap; if the versions in requirements.txt
differ from whats installed in the snap from Ubuntu core then the snap
fails to build.
Closes-Bug: #1908610
Change-Id: I83d623db3a8d3cd8f328b42da4aff5b71f2f0520