tools: Introduce install-nss targets
    
    We do have something similar for installing init system files.
    Basically I'm trying to avoid the following warning produced by
    automake:
    
    tools/Makefile.am:429: warning: uninstall-local was already defined in condition TRUE, which includes condition WITH_BSD_NSS ...
    tools/Makefile.am:292: ... 'uninstall-local' previously defined here
    
    Signed-off-by: Michal Privoznik <mprivozn@redhat.com>