Add additional log of meta_data devices content

In TaggedAttachmentsTest.test_tagged_attachment test there is
now added some additional debug log to check what
devices are still in meta_data's devices field when it should
be empty already.

This patch changes also from handling all exeptions to only
AssertionError in verify_empty_devices() method.
If exeption other than AssertionError occur, it will not be silently
ignored anymore.

Change-Id: I95016e35102569fba79fc58f9695e480234619dc
Related-Bug: #1775947
1 file changed