Update the android bot to Ubuntu 16.04
Update the android bot to Ubuntu 16.04

This gives us CMake > 2.8 and should hopefully help fixing rust-lang/rust#34559

rust-lang-deprecated/rust-buildbot,rust-lang/rust-buildbot,rust-lang/rust-buildbot,rust-lang/rust-buildbot,rust-lang-deprecated/rust-buildbot,rust-lang-deprecated/rust-buildbot