Kibana version: 7.14

Describe the bug: It's possible to "save" a session even if courier:batchSearches is enabled which effectively disables the whole async search process.

Steps to reproduce:

1. Set courier:batchSearches in advanced settings
2. Go to Discover
3. Save the session
4. Go to session management
5. Sasved session with 0 searches "in progress" is shown

Expected behavior:
It shouldn't be possible to save the session

Screenshots (if relevant):