[ticket/11445] optimize no of queries in get_global_subscriptions( )
* dhruvgoel92/ticket/11445:
[ticket/11445] Move get user's notification code into its own method
[ticket/11445] Remove unused foreach key $group_name
[ticket/11445] Improve unit tests for get_global_subscriptions
[ticket/11445] Optimize no of queries in get_global_subscriptions