filter_missing_packages expects a list and not a single package name as
a string. Pass the chrony package as a single item list to avoid it
checking installation candiates for 'c', 'h', 'r', 'o', 'n' and 'y'
This patch simplifies the function, which makes it a little easier to
reason about. Also a test is added to stop regressions in the future.
[1] Ie3c9c5899c1d46edd21c32868938d3290db321e7
[2] Ifef76eacd8bd837d2181ec75e406aa35f88b8b5b
Closes-Bug: #1929054
Change-Id: I93f53274bc8c7e62ebb8cb7bf81ff816f4bfd98b
Helper functions for the ceph charms. This library has shared functionality that is used in the ceph-mon, ceph-osd and ceph
charms. Anything that needs to be shared across the ceph charms should live here.