ref(rules): Remove inner lock and add logging on exception

[ceorourke]

Part of debugging the delayed rule processor lead here, we don't need the inner lock (it's locked here before process_batch is called).

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 0% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 80.04%. Comparing base (82eeb04) to head (c2134c1). Report is 6 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master   #70629   +/-   ##
=======================================
  Coverage   80.04%   80.04%           
=======================================
  Files        6502     6502           
  Lines      290537   290533    -4     
  Branches    50068    50066    -2     
=======================================
+ Hits       232547   232552    +5     
+ Misses      57552    57543    -9     
  Partials      438      438           

Files	Coverage Δ
src/sentry/buffer/redis.py	92.07% <0.00%> (-0.41%)	:arrow_down:

... and 15 files with indirect coverage changes