linux: Adjust test_bluetooth_le_device for dbusmock 0.30.1
dbusmock 0.30.1 changed the BlueZ template to set the default "Class"
property to MOCK_PHONE_CLASS
right away instead of in PairDevice() [1].
test_bluetooth_le_device() relied on the previous implicit default of a "0" Class value. Set this explicitly to expect a "generic" device. This makes the test work with old and current dbusmock versions.
https://bugs.debian.org/1059467
[1] https://github.com/martinpitt/python-dbusmock/pull/192
I can locally reproduce the regression and confirm that the test is happy with both dbusmock 0.30.0 and current 0.30.1.