testing/anbox: upgrade to 20200303 and fix issues

This commit upgrades to 3rd march master, and address the following:

• repair and enable unit tests.

• add icon.

• drop arm build patch as it was merged upstream.

• drop armhf architecture as there is no android image anyway for this arch.

• drop anbox-networkmanager subpackage: it isn't needed anymore as the iptable script requirement are better known.

• remove files from a dependency that got installed to /usr/include, as they don't belong to the package (it probably should be removed and split to another package altogether).

• add root shell script.