Use call_soon() when closing in conn._read_data()

[honzasp]

Addresses issue #292

[codecov]

Codecov Report

Merging #301 into master will increase coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #301      +/-   ##
==========================================
+ Coverage   96.83%   96.84%   +0.01%     
==========================================
  Files          59       59              
  Lines        7553     7553              
  Branches      599      599              
==========================================
+ Hits         7314     7315       +1     
- Misses        174      175       +1     
+ Partials       65       63       -2

Impacted Files	Coverage Δ
tests/sentinel_failover_test.py	87.21% <0%> (+0.75%)	⬆️

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[popravich]

Thanks