costmap_cspace: always store received overlay map

[at-wat]

If an overlay map arrives before a root map, overlay map was ignored
since frame_id of the root map is not yet given.
The commit enables to always store overlay map and keep until receiving
the root map.

[at-wat]

PASSED

All tests passed

Skipping "src/neonavigation/neonavigation_launch/package.xml": 'tests'
Skipping "src/neonavigation/map_organizer/package.xml": 'tests'
Skipping "src/neonavigation/safety_limiter/package.xml": 'tests'
Skipping "src/neonavigation/track_odometry/package.xml": 'tests'
Skipping "src/neonavigation/costmap_cspace/package.xml": 'tests'
Skipping "src/neonavigation/trajectory_tracker/package.xml": 'tests'
Skipping "src/neonavigation/obj_to_pointcloud/package.xml": 'tests'
Skipping "src/neonavigation/neonavigation/package.xml": 'tests'
Skipping "src/neonavigation/planner_cspace/package.xml": 'tests'
build/test_results/costmap_cspace/gtest-test_costmap_3d.xml: 6 tests
build/test_results/costmap_cspace/roslint-costmap_cspace.xml: 1 tests
build/test_results/map_organizer/roslint-map_organizer.xml: 1 tests
build/test_results/obj_to_pointcloud/roslint-obj_to_pointcloud.xml: 1 tests
build/test_results/planner_cspace/gtest-test_blockmem_gridmap.xml: 2 tests
build/test_results/planner_cspace/gtest-test_blockmem_gridmap_performance.xml: 1 tests
build/test_results/planner_cspace/gtest-test_cyclic_vec.xml: 7 tests
build/test_results/planner_cspace/roslint-planner_cspace.xml: 1 tests
build/test_results/planner_cspace/rostest-test_test_navigation_rostest.xml: 1 tests
build/test_results/planner_cspace/rosunit-test_navigate.xml: 1 tests
build/test_results/safety_limiter/roslint-safety_limiter.xml: 1 tests
build/test_results/track_odometry/gtest-tf_projection_test.xml: 1 tests
build/test_results/track_odometry/roslint-track_odometry.xml: 1 tests
build/test_results/trajectory_tracker/roslint-trajectory_tracker.xml: 1 tests
Summary: 26 tests, 0 errors, 0 failures, 0 skipped