Implement support for event-driven notifications in stratisd
Implement support for event-driven notifications in stratisd

If an engine provides an Eventable, don't call check every 10 seconds.
Instead sleep indefinitely until D-Bus requests or a device notification
wake us up. This is made more complicated because the D-Bus fds may
change over time, and because Eventable is only optionally provided.
If one isn't provided, continue to wake up every 10 seconds to call
check(), as before.

Signed-off-by: Andy Grover <b7d524d2f5cc5aebadb6b92b08d3ab26911cde33@redhat.com>

stratis-storage/stratisd,trgill/stratisd,stratis-storage/stratisd,mulkieran/stratisd,stratis-storage/stratisd,trgill/stratisd,mulkieran/stratisd