p2p: fix race in dialScheduler

[ucwong]

No description provided.

[codecov]

Codecov Report

Attention: Patch coverage is 87.50000% with 3 lines in your changes are missing coverage. Please review.

Project coverage is 47.26%. Comparing base (c2de451) to head (f019a85).
Report is 26 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1944      +/-   ##
==========================================
- Coverage   47.28%   47.26%   -0.03%     
==========================================
  Files         568      568              
  Lines       68852    68859       +7     
==========================================
- Hits        32560    32548      -12     
- Misses      33767    33779      +12     
- Partials     2525     2532       +7     

Files	Coverage Δ
p2p/dial.go	88.88% <87.50%> (-0.10%)	⬇️

... and 10 files with indirect coverage changes