Reset JTC PID's to zero on_activate() (backport #1840)

[mergify]

When running the JTC in velocity control mode I noticed that the joints receive an impulse on reactivation after is has thrown a previous fault in motion. In the below example you can see this joint gets an impulse of -4 rad/sec down to zero as I reactivate the JTC. The impulse causes my hardware to throw another fault.

This change adds a reset() call to each joints PID controller so that the old command values are zero'd out when (re)activating.

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This is an automatic backport of pull request #1840 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of 18c9f1f has failed:

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	both modified:   joint_trajectory_controller/src/joint_trajectory_controller.cpp

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 67.09%. Comparing base (4aa06d7) to head (9df9020).
⚠️ Report is 4 commits behind head on humble.

Additional details and impacted files

@@           Coverage Diff           @@
##           humble    #1843   +/-   ##
=======================================
  Coverage   67.09%   67.09%           
=======================================
  Files         122      122           
  Lines       14546    14548    +2     
  Branches     8984     8987    +3     
=======================================
+ Hits         9759     9761    +2     
  Misses       1461     1461           
  Partials     3326     3326           

Flag	Coverage Δ
unittests	67.09% <100.00%> (+<0.01%)	⬆️

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Files with missing lines	Coverage Δ
...ory_controller/src/joint_trajectory_controller.cpp	81.97% <100.00%> (+0.04%)	⬆️

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