Change default pidfile from redis.pid to valkey.pid

[Shivshankar-Reddy]

Changes the default value for the pidfile config.

The template config file valkey.conf already contains pidfile /var/run/valkey_6379.pid. This is not a default. The default is what you get when you start valkey without config.

Tests suites config pidfile changed to valkey accordingly.

Fixes #321

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 68.40%. Comparing base (52f9291) to head (db63a87).
Report is 10 commits behind head on unstable.

Additional details and impacted files

@@            Coverage Diff            @@
##           unstable     #378   +/-   ##
=========================================
  Coverage     68.40%   68.40%           
=========================================
  Files           108      108           
  Lines         61562    61562           
=========================================
  Hits          42109    42109           
  Misses        19453    19453           

see 10 files with indirect coverage changes

[Shivshankar-Reddy]

@zuiderkwast, Can you check this PR when you get some time?

[zuiderkwast]

Good!

pidfile /var/run/valkey_6379.pid was already written in the template config file valkey.conf. This is not a default. It is a value you get if you use the template config as is. The default is what you get when you start without a config.