Fix ARM releases to be quantal armv7l releases.
Made grub execution conditional and not done when ARM.
Use ctx parameter to change machine type to tala.
Fix kernel assignments when running ARM systems.

Fixes: #5000
Signed-off-by: Warren Usui <warren.usui@inktank.com>
Merge pull request #42 from ceph/wip-arm5000-wusui

Fix ARM releases to be quantal armv7l releases.