Update submodule libuavcan to latest Thu Aug 16 15:14:07 EDT 2018

    - libuavcan in PX4/Firmware (9c9160e015aa68ee7efe456dae7de6fc9a819715): https://github.com/UAVCAN/libuavcan/commit/3ca697e64d52ba86c8e831d563c746827473e5e3
    - libuavcan current upstream: https://github.com/UAVCAN/libuavcan/commit/aa3650d34d9732af51ced52add24dee044eac79a
    - Changes: https://github.com/UAVCAN/libuavcan/compare/3ca697e64d52ba86c8e831d563c746827473e5e3...aa3650d34d9732af51ced52add24dee044eac79a

    aa3650d 2018-08-16 Pavel Kirienko - Merge pull request #156 from UAVCAN/master_kinetis_flexcan
0dc5751 2018-07-30 Pavel Kirienko - Merge pull request #155 from hjoertel/change-start-script
ff040ea 2018-07-30 Oertel - removed the confusing "echo ..." line (it confused Pavel)
8bb5677 2018-07-30 Oertel - replaced the depricated ifconfig command by the ip command

libuavcan @ aa3650d3

-Subproject commit 3ca697e64d52ba86c8e831d563c746827473e5e3
+Subproject commit aa3650d34d9732af51ced52add24dee044eac79a