have docker autodetect if it is running on arm

[Jamie Strandboge]

From the mailing list:
https://lists.ubuntu.com/archives/snappy-app-devel/2015-June/000253.html

[Dustin Kirkland  (kirkland)]

Specifically:

>> FYI, if using docker on arm you need to use '-t armbuild/ubuntu:trusty' instead
>> of '-t ubuntu:trusty'.
> Can we please patch docker to detect and handle that automatically?

I have to look up '-t armbuild/ubuntu:trusty' all the time :-)

[Leo Arias (elopio)]

I can't reproduce this because I get an error earlier:

ubuntu@localhost:~$ docker
/snaps/docker/1.6.2.005-16.04.1-2/bin/docker: line 4: /home/ubuntu/bin/bin_arch: No such file or directory
/snaps/docker/1.6.2.005-16.04.1-2/bin/docker: line 11: select_bin: command not found

looks also related to arch.

Tested in beaglebone black:
ubuntu@localhost:~$ snappy list
Name Date Version Developer
beagleblack 2016-02-03 3.0 mvo
docker 2016-03-03 1.6.2.005-16.04.1-2 canonical
linux-armhf 2016-02-22 4.4.0-6-1 mvo
ubuntu-core 2016-03-21 16.04+20160321.17-37 canonical