ipa_pwd: remove unnecessary dependency on dirsrv plugins
    
    "dirsrv/slapi-plugin.h" is unnecessary for build of ipa_pwd.
    This patch allow us to move DIRSRV to daemon only dependencies
    
    Reviewed-By: Simo Sorce <ssorce@redhat.com>
    Reviewed-By: Tomas Krizek <tkrizek@redhat.com>