Remove obsolete linaro-apm-* slaves and replace them with
per-slave docker containers on new 96-core linaro-thx1-01 machine.
Once we confirm that linaro-thx1-01 is as stable as linaro-armv8-01,
we are going to migrate all linaro-*-aarch64-* bots to linaro-thx1-01
and leave linaro-armv8-01 to service only armv8 (aarch32) bots.