Merge pull request #2059 from chikoon/CLC-3187-forced-cache-write-warmup

CLC-3187: LiveUpdates: Do warmup in a forced-cache-write mode
NOJIRA My Classes dummy JSON was never updated to include current_term from CLC-2218
Also fixed misleading "source" for Canvas group
CLC-2498 Untangle My Classes and My Groups sites implementation
To support addition of sites to My Academics
CLC-2498 Fix testext
Merge pull request #2061 from raydavis/raywip

CLC-2498 Untangle My Classes and My Groups sites implementation
CLC-3187-ii: LiveUpdates: eliminate MERGED_FEEDS_EXPIRATION

https://jira.media.berkeley.edu/jira/browse/CLC-3187

Deleted MERGED_FEEDS_EXPIRATION instance of UserCacheInvalidator.

Since UserCacheWarmer now forces write to the cache, there's no
need to expire the cache on merged feeds via observers.

 i then also delete MERGED_FEEDS_EXPIRATION from the cache cache_tools initializer