Startup channel monitor when a channel is restarted

[dirkmc]

Fixes #268

[codecov-commenter]

Codecov Report

Merging #269 (4707684) into master (3260d19) will increase coverage by 0.06%.
The diff coverage is 33.33%.

@@            Coverage Diff             @@
##           master     #269      +/-   ##
==========================================
+ Coverage   67.77%   67.83%   +0.06%     
==========================================
  Files          24       24              
  Lines        3131     3137       +6     
==========================================
+ Hits         2122     2128       +6     
- Misses        649      650       +1     
+ Partials      360      359       -1     

Impacted Files	Coverage Δ
impl/restart.go	61.79% <33.33%> (-2.06%)	⬇️
network/libp2p_impl.go	67.53% <0.00%> (+2.59%)	⬆️

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[aarshkshah1992]

lgtm