fix max query depth tracking

[bluejekyll]

The original patch to this issue was incorrect.
This better, it relies on the task cleanup to remove the QUERY_DEPTH, thus we only need to track the increments.

also fixes the global resolver example to fail if the tests fail.

[codecov]

Codecov Report

Merging #469 into master will decrease coverage by 0.02%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #469      +/-   ##
==========================================
- Coverage   86.53%   86.51%   -0.03%     
==========================================
  Files         133      133              
  Lines       13428    13429       +1     
==========================================
- Hits        11620    11618       -2     
- Misses       1808     1811       +3

Impacted Files	Coverage Δ
resolver/src/lookup_state.rs	92.64% <100%> (+0.01%)	⬆️
proto/src/multicast/mdns_stream.rs	79.88% <0%> (-0.85%)	⬇️

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