Call 'setpwent' to rewind to the beginning of the passwd database.

--- src/greeter/UserModel.cpp.orig	2016-07-10 21:26:13 UTC
+++ src/greeter/UserModel.cpp
@@ -55,6 +55,7 @@ namespace SDDM {
         const QString defaultFace = QStringLiteral("%1/.face.icon").arg(facesDir);

         struct passwd *current_pw;
+        setpwent();
         while ((current_pw = getpwent()) != nullptr) {

             // skip entries with uids smaller than minimum uid