Simplify on_set_chained_mode avoiding cpplint warnings (backport #1564)

[mergify]

Fixed warnings generated by cpplint/cpplint#131 on some of the controllers that implement the chained mode.

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This is an automatic backport of pull request #1564 done by Mergify.

[mergify]

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Changes to be committed:
	modified:   mecanum_drive_controller/src/mecanum_drive_controller.cpp
	modified:   steering_controllers_library/src/steering_controllers_library.cpp

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   diff_drive_controller/src/diff_drive_controller.cpp
	both modified:   pid_controller/src/pid_controller.cpp

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