Log AttributeError as 'info' instead of 'exception'

When failure happens in setUpClass, tearDownclass is being called
from base class irrespective of safe_setup decorator used or not in
specific test class. Which results to lot of instance of AttributeError
raised from tearDownclass. For example when tests case is skipped.

This patch provides a workaround by logging AttributeError as 'info'
instead of 'exception'.

Permanent fix for cleaning up those in more appropriate way will
be by split-up resource_setup & resource_cleanup in more structural way
as part of second phase of resource cleanup BP.

Change-Id: Ia49c9e171338e22f8d605fc53d251ef3d3471bb1
Merge "Log AttributeError as 'info' instead of 'exception'"