Reminder's state manager stale value with more than one run through

## Expected Behavior
Reminder that goes beyond one cycle (isn't removed after one single run through) should get an update to state eventually.

## Actual Behavior
Reminder never receives an updated state if state is updated following the first run through.

## Steps to Reproduce the Problem
Run example/actor demo app. Modify so that state is updated by ActorClient once the reminder had a chance to read state at least once. Notice how on subsequent runs (second, third, etc...) even though the reminder calls StateManager.GetStateAsync<> it never gets an update.

Repo showing code changes to reproduce:
https://github.com/tstojecki/dotnet-sdk/commits/reminder-stale-cache-state-bug

## Release Note
RELEASE NOTE:
**FIX** Bug in reminder's state manager never getting an updated state.