Fix compile warnings

[syohex]

I got following compile warnings.

/home/syohei/work/Autoware/ros/src/data/packages/map_db/lib/map_db/GetFile.cpp: In member function ‘int GetFile::ConnectHTTP()’:
/home/syohei/work/Autoware/ros/src/data/packages/map_db/lib/map_db/GetFile.cpp:64:6: warning: unused variable ‘r’ [-Wunused-variable]
  int r;
      ^
/home/syohei/work/Autoware/ros/src/data/packages/map_db/lib/map_db/GetFile.cpp: In member function ‘int GetFile::GetHTTPFile(const string&)’:
/home/syohei/work/Autoware/ros/src/data/packages/map_db/lib/map_db/GetFile.cpp:170:6: warning: unused variable ‘r_head’ [-Wunused-variable]
  int r_head = 1;
      ^
/home/syohei/work/Autoware/ros/src/data/packages/map_db/lib/map_db/GetFile.cpp:164:41: warning: ignoring return value of ‘ssize_t write(int, const void*, size_t)’, declared with attribute warn_unused_result [-Wunused-result]
  write(sock, send_buf, strlen(send_buf));
                                         ^
/home/syohei/work/Autoware/ros/src/data/packages/map_db/lib/map_db/GetFile.cpp:166:41: warning: ignoring return value of ‘ssize_t write(int, const void*, size_t)’, declared with attribute warn_unused_result [-Wunused-result]
  write(sock, send_buf, strlen(send_buf));
                                         ^
/home/syohei/work/Autoware/ros/src/data/packages/map_db/lib/map_db/GetFile.cpp:168:41: warning: ignoring return value of ‘ssize_t write(int, const void*, size_t)’, declared with attribute warn_unused_result [-Wunused-result]
  write(sock, send_buf, strlen(send_buf));
                                         ^
/home/syohei/work/Autoware/ros/src/data/packages/map_db/lib/map_db/GetFile.cpp:192:2: warning: ‘i’ may be used uninitialized in this function [-Wmaybe-uninitialized]
  for(int i; i < 10; i++) {
  ^

...

/home/syohei/work/Autoware/ros/src/computing/planning/motion/packages/driving_planner/nodes/lattice_trajectory_gen/lattice_trajectory_gen.cpp:402:29: warning: ‘geometry_msgs::Twist calcTwist(int)’ defined but not used [-Wunused-function\
]
 static geometry_msgs::Twist calcTwist(int next_waypoint)
                             ^
Linking CXX executable /home/syohei/work/Autoware/ros/devel/lib/driving_planner/lattice_trajectory_gen
[ 98%] Built target lattice_trajectory_gen
Scanning dependencies of target lattice_twist_convert
[ 98%] Building CXX object computing/planning/motion/packages/driving_planner/CMakeFiles/lattice_twist_convert.dir/nodes/lattice_twist_convert/lattice_twist_convert.cpp.o
/home/syohei/work/Autoware/ros/src/computing/planning/motion/packages/driving_planner/nodes/lattice_twist_convert/lattice_twist_convert.cpp: In function ‘void splineCallback(const ConstPtr&)’:
/home/syohei/work/Autoware/ros/src/computing/planning/motion/packages/driving_planner/nodes/lattice_twist_convert/lattice_twist_convert.cpp:212:12: warning: unused variable ‘start_time’ [-Wunused-variable]
     double start_time = ros::Time::now().toSec();
            ^