update robot state transforms when initializing a planning scene

[mlautman]

Description

There was a bug in moveit_visual_tools where adding a collision object after initializing the planning scene resulting in the following error: robot_state.cpp:998: const Isometry3d& moveit::core::RobotState::getFrameTransform(const string&) const: Assertion checkLinkTransforms()' failed.`

This error is caused by the robot state in the planning scene holding dirty link transforms after initialization.

This PR fixes the underlying issue

Checklist

• Required by CI: Code is auto formatted using clang-format
• Extended the tutorials / documentation, if necessary reference
• Include a screenshot if changing a GUI
• Document API changes relevant to the user in the moveit/MIGRATION.md notes
• Created tests, which fail without this PR reference
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