Update lifecycle_manager_client.cpp

Fix build error under clang:
```
--- stderr: nav2_lifecycle_manager                                                                                                
/opt/ros/master/src/ros-planning/navigation2/nav2_lifecycle_manager/src/lifecycle_manager_client.cpp:149:5: error: cannot pass object of non-trivial type 'std::string' (aka 'basic_string<char>') through variadic function; call will abort at runtime [-Wnon-pod-varargs]
    service_name_);
    ^
/opt/ros/master/src/ros-planning/navigation2/nav2_lifecycle_manager/src/lifecycle_manager_client.cpp:160:5: error: cannot pass object of non-trivial type 'std::string' (aka 'basic_string<char>') through variadic function; call will abort at runtime [-Wnon-pod-varargs]
    service_name_);
    ^
2 errors generated.
```