Update availability-zone to use the flag instead of the number 0

[enjoy-binbin]

Minor cleanup.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 70.27%. Comparing base (1269532) to head (38a5845).
Report is 1 commits behind head on unstable.

Additional details and impacted files

@@             Coverage Diff              @@
##           unstable     #711      +/-   ##
============================================
+ Coverage     70.23%   70.27%   +0.03%     
============================================
  Files           111      111              
  Lines         60203    60206       +3     
============================================
+ Hits          42286    42308      +22     
+ Misses        17917    17898      -19     

Files	Coverage Δ
src/config.c	78.39% <ø> (ø)

... and 14 files with indirect coverage changes