Fix memory leak in the ros2_control

[saikishor]

For some reason, the get_name method that is returning by copy is creating various mallocs in the RT loop and this is causing slight memory leaks.

gdb with breakpoint on malloc, brings me to these logs, so it would be nice to have this sorted to not have allocations in the RT loop

#2  0x00007f71817f5cdd in ?? () from //lib/librobot_control.so
#3  0x00007f718580eb29 in hardware_interface::System::get_name[abi:cxx11]() const () from lib/libhardware_interface.so
#4  0x00007f71857ebc62 in ?? () from lib/libhardware_interface.so
#5  0x00007f71857edd20 in hardware_interface::ResourceManager::read(rclcpp::Time const&, rclcpp::Duration const&) () from lib/libhardware_interface.so
#6  0x00007f718608b5de in controller_manager::ControllerManager::read(rclcpp::Time const&, rclcpp::Duration const&) () from lib/libcontroller_manager.so
#7  0x000055dd43023c26 in ?? ()
#8  0x00007f7185c38253 in ?? () from /lib/x86_64-linux-gnu/libstdc++.so.6
#9  0x00007f71859a7ac3 in start_thread (arg=<optimized out>) at ./nptl/pthread_create.c:442
#10 0x00007f7185a39850 in clone3 () at ../sysdeps/unix/sysv/linux/x86_64/clone3.S:81
```

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.37%. Comparing base (2dc3725) to head (194e869).
Report is 4 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2033      +/-   ##
==========================================
+ Coverage   89.33%   89.37%   +0.04%     
==========================================
  Files         138      138              
  Lines       14772    14762      -10     
  Branches     1270     1270              
==========================================
- Hits        13196    13193       -3     
+ Misses       1100     1092       -8     
- Partials      476      477       +1     

Flag	Coverage Δ
unittests	89.37% <100.00%> (+0.04%)	⬆️

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

Files with missing lines	Coverage Δ
..._interface/include/hardware_interface/actuator.hpp	100.00% <ø> (ø)
.../include/hardware_interface/actuator_interface.hpp	91.15% <100.00%> (-0.82%)	⬇️
...rface/include/hardware_interface/hardware_info.hpp	100.00% <100.00%> (ø)
...re_interface/include/hardware_interface/sensor.hpp	100.00% <ø> (ø)
...ce/include/hardware_interface/sensor_interface.hpp	90.90% <100.00%> (-4.48%)	⬇️
...re_interface/include/hardware_interface/system.hpp	100.00% <ø> (ø)
...ce/include/hardware_interface/system_interface.hpp	81.81% <100.00%> (ø)
hardware_interface/src/actuator.cpp	80.66% <100.00%> (ø)
hardware_interface/src/sensor.cpp	76.03% <100.00%> (ø)
hardware_interface/src/system.cpp	80.66% <100.00%> (ø)
... and 3 more

[Juliaj]

LGTM.

[arne48]

LGTM