Fix failing test_snap_set_and_get_with_typed integration test

[benhoyt]

This is failing with an error connecting to the snapd socket:

tests/integration/test_snap.py::test_snap_set_and_get_with_typed 
-------------------------------- live log call ---------------------------------
INFO     charms.operator_libs_linux.v2.snap:snap.py:590 Refreshing snap lxd, revision None, tracking latest
error: cannot perform the following tasks:
- Run configure hook of "lxd" snap if present (run hook "configure": error: cannot communicate with server: \
    Post "http://localhost/v2/snapctl": dial unix /run/snapd-snap.socket: connect: no such file or directory)
FAILED

Other similar tests seem to be succeeding.