policy-device-profile: Don't restore if active profile is persistent and default

Currently, if the current device profile is defined as persistent (eg off), and a new profile with higher priority becomes available, wireplumber will never auto-switch to it. This causes a problem when the current profile has been automatically switched to a persistent profile (eg off on suspend), because the device will never be recovered when a new one with higher priority becomes available (eg on resume).

To fix this issue with persistent profiles, we only auto-switch to a higher profile available if the persistent profile is the default saved profile (manually set by the user).

Fixes #204 (closed)