Set the horizontal angular velocity to zero

[tongtybj]

I think the angular velocity regarding to x and y axis is useless, in the case of 2d mapping.
Maybe these values are omitted in the latest cartographer if use_trajectory_builder_2d is true.

However, we are trying to use the debianized cartographer in ros kinetic distro, which is based on version 0.2.0, and I found that the horizontal angular velocity effects significantly on the localization as shown in the following GIF.

After applying this commit, the localization is improved a lot as shown in the following GIF.

Please think about to merge this commit.

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[gaschler]

Seems to improve the published pose (most likely PoseExtrapolator results in cartographer_ros are improved).
I don't see much change in the map.