Add sleep for check_signature

[sakridge]

Problem

check_signature loops at the fastest speed to check for signatures causing overhead on server and client. Also, it never exits which is a problem when you are talking to a server which may be down or unavailable.

Summary of Changes

Add sleep to loop and fixed number of iterations.

Fixes #

[codecov]

Codecov Report

Merging #3677 into master will decrease coverage by <.1%.
The diff coverage is 33.3%.

@@           Coverage Diff            @@
##           master   #3677     +/-   ##
========================================
- Coverage    79.6%   79.6%   -0.1%     
========================================
  Files         155     155             
  Lines       24863   24865      +2     
========================================
+ Hits        19805   19806      +1     
- Misses       5058    5059      +1

[CriesofCarrots]

I'm fine with this. Definitely an improvement. (However, it's obvious that rpc_client needs some reconstructive surgery. It's a mish-mash of methods scraped from rpc and thin_client, and retry handling is all over the place 🤢 )

[sakridge]

@CriesofCarrots agreed