Fix tools/xen/functions for bashate errors

Change I205d675ff231c0403dd135eacc8d57b45317859f modified the matching
for bashate and it has started running on this file, whereas before it
wasn't.  This fixes the errors it is now picking up.

(cherry picked from commit 62cae13d7e7e13102a02aa385ae63b8e2afb7c83)

(We need to squash these 2 patches together to pass tests)

Use tox for bashate testing

Create a tox.ini file to install bashate into a virtualenv for running
tests. It can be run with a command such as "tox -v -ebashate". The find
command being used is equivalent to the default list of files discovered
by bashate plus the exclusion of the .tox/ directory. Also add the .tox/
directory to the .gitignore file.

Conflicts:
	.gitignore

Change-Id: I7876b5c94d90f15e3b0228999c0750bfbebcaa1c
(cherry picked from commit 0c256abd766265b8fdb11d354be7115c05bcaeb5)