Remove the NSS_LIBS and KRB5_LIBS variables from sssd.spec
    
    Due to the way RPM processes the %configure macro, these variables
    were not actually being passed down to recursive configure
    invocations. In other words, they were useless.
    
    Futhermore, in more recent Fedora versions (13+), some of the
    dependencies have moved from -lnss to -lnspr4. As a result, it is
    safer to rely on the complete output of 'pkg-config nss --libs'
    instead of restricting to -lnss. The downside to this is that it
    may result in linking unnecessarily against other NSS components
    such as libsmime3 and libplc4 (among others). However, since these
    are already dependencies of libnss itself, there should be no risk
    of them being unavailable on the platform when installed.