Only restart Cassandra on config-changed when the config has actually changed.
Merged evs mp
[ev,r=dames] Stop random cassandra restarts
[dspiteri] add an extra repo and packages c#63545
[DarrenS,r=gnuoy] add an extra repo and packages c#63545
[dspiteri] clear config.yaml
[dspiteri] remove redundant extra apt source
[dspiteri,r=mthaddon] remove redundant apt source
config for an extra package to be installed
[dspiteri] config for an extra package to be installed
Stop random cassandra restarts, config for an extra package to be installed
merging lp:~dspiteri/charms/precise/cassandra/prodchanges as per https://code.launchpad.net/~dspiteri/charms/precise/cassandra/prodchanges/+merge/179862