Reset the async handler variables to handle exceptions properly

[saikishor]

Exception handling is recently added to AsyncFunctionHandler : ros-controls/realtime_tools#172

Right now, if the exception is thrown and the variables are not reset, activating the controller will continue to throw an exception unless it is properly reset. For this to work properly, the user is forced to reconfigure his controller and then activate it.

[codecov]

Codecov Report

Attention: Patch coverage is 75.00000% with 1 line in your changes missing coverage. Please review.

Project coverage is 87.99%. Comparing base (d714e8b) to head (d7efc8c).
Report is 3 commits behind head on master.

Files with missing lines	Patch %	Lines
...roller_interface/src/controller_interface_base.cpp	75.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1860      +/-   ##
==========================================
- Coverage   88.01%   87.99%   -0.02%     
==========================================
  Files         121      121              
  Lines       12403    12406       +3     
  Branches     1108     1109       +1     
==========================================
+ Hits        10916    10917       +1     
  Misses       1083     1083              
- Partials      404      406       +2     

Flag	Coverage Δ
unittests	87.99% <75.00%> (-0.02%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
...roller_interface/src/controller_interface_base.cpp	85.36% <75.00%> (-0.72%)	⬇️

... and 1 file with indirect coverage changes