aa-cleanprof / delete_duplicates() doesn't check indirect includes

[Christian Boltz]

aa-cleanprof / delete_duplicates() checks only files directly included in a profile, but it doesn't check indirect includes.

Shortened example:

usr.sbin.dovecot {
    # include <abstractions/nameservice>
    capability net_bind_service,
}

abstractions/nameservice contains:
    #include <abstractions/nis>

abstractions/nis contains:
    capability net_bind_service,

Expected result: aa-cleanprof should remove net_bind_service from the dovecot profile.

-> delete_duplicates() in aa.py needs to recursively(!) check the includes