agent: Don't distribute compiled dbus sources

This causes build problems due to gdbus-codegen's brokenness.

Closes #480
Reviewed-by: Marius Vollmer <marius.vollmer@redhat.com>
common: Add missing dirent.h header

This caused build failures on some non-Fedora systems.

Closes #481
Reviewed-by: Marius Vollmer <marius.vollmer@redhat.com>