Fixing documentation for call collect

The documentation mentioned "collect call", however the server
is sending "collect_calls". Fixed the documentation so it matches
reality.

PS This was correct in the older documentation, somehow it got
changed.

(cherry picked from commit 04e9217e2e3f9c47d7a62821a34b93206c90dde6)
Add documentation for process table cache in state dir

(cherry picked from commit 04393a424c0dd0c21f56e978eebd8e7495b3c686)