Added image tag variable, Updated Arch detection

Got rid of the ubuntu to latest check and added a new variable imgtag.
If people want to specify the image tag they can use this otherwise it
defaults to using latest. This change carries on in building the image.
In addition updated the arch detection to use the newer one that looks
much cleaner and makes more sense. Updated a few comments to make them
more understandable. Added architecture to the tag of the build image.

Change-Id: I3f100d46616dd29b175e5135e0da6076681a5cb3
Signed-off-by: Alanny Lopez <alanny.lopez@ibm.com>
1 file changed