tools: append new line to string from poptStrerror()
https://fedorahosted.org/sssd/ticket/1756
Messages from poptStrerror() passed to BAD_POPT_PARAMS macro were
printed out to the console without new line character at the end of the
message. BAD_POPT_PARAMS should now behave correctly with strings both
with or without new line character at the end.