Bug 594745 - Get rid of dirsrv_lib_t label
    
    The dirsrv_lib_t label used to label the dirsrv libraries is causing
    AVCs to occur from prelink.  It turns out that the dirsrv_lib_t
    label is not really necessary.  We can just allow our libraries to
    use the default label of lib_t.
    
    This patch simply stops using the dirsrv_exec_lib macro since that
    macro has been removed from the dirsrv policy interface as part of
    the elimination of the dirsrv_lib_t label.