Before this change there was a need to keep addhost and
bootstrap-cosmos.sh in sync regarding what version of the cosmos deb to
scp over and later run.
Now we find the latest version as decided by `sort -V` in both addhost
and bootstrap-cosmos.sh.
Solution discussed with @fredrikt.
Good idea to fail when unexpected things go wrong. Additional fixes
added to the script to not stop where we can expect a non-zero return
code.
Requested by @fredrikt who also reviewed the patch before going in,
thanks!