Refactor puller ipc timeout

[gfieni]

PR overview:

• Uses the socket_interface global timeout instead of the fixed 0.1 second value for receive_control method ;
• Adds a FakeDispatcher class for the tests ;
• Improves the Puller unit tests with more concrete tests cases.

[codecov]

Codecov Report

Merging #155 (553913c) into master (5999793) will increase coverage by 0.00%.
The diff coverage is 0.00%.

❗ Current head 553913c differs from pull request most recent head a3ec169. Consider uploading reports for the commit a3ec169 to get more accurate results

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #155   +/-   ##
=======================================
  Coverage   60.69%   60.70%           
=======================================
  Files          85       85           
  Lines        3132     3130    -2     
=======================================
- Hits         1901     1900    -1     
+ Misses       1231     1230    -1     

Impacted Files	Coverage Δ
powerapi/actor/actor.py	52.04% <ø> (+0.04%)	⬆️
powerapi/puller/handlers.py	27.67% <0.00%> (ø)
powerapi/puller/puller_actor.py	92.59% <0.00%> (ø)