test: Python import cleanup

test: Python import cleanup

Some test scripts use "from gi.repository import GObject" whereas others
use "import gobject". gi.repository is not always available on embedded
systems, so convert all instances to this format:

try:
  from gi.repository import GObject
except ImportError:
  import gobject as GObject

Also, sort the imports in this order: system, dbus, gobject, bluezutils