Make sure the nolog argument to ipautil.run is not a bare string
ipautil.run expects a tuple of passwords for nolog; passing a
single string causes all individual letters from that string to
be replaced by Xes.
This fixes such a call, and adds a sanity check to ipautil.run
that prevents lone strings from being used in nolog.
https://fedorahosted.org/freeipa/ticket/2419