B #5946: Fix parsing * in the group list (#2261)

Regression introduced by68ce7dc0 

With the addition to skipws, peek() will read the next whitespace in the buffer. The logic has been changed to use the extraction operator so ws are consumed. The peek - get is now changed by >> - unget calls

src/um/UserPool.cc

@@ -589,13 +589,18 @@ static int parse_auth_msg(
         int  tmp_gid;
         bool gr_admin = false;
 
-        char c = is.peek();
+        char c;
+
+        is >> c;
 
         if ( c == '*' )
         {
-            is.get(c);
             gr_admin = true;
         }
+        else
+        {
+            is.unget();
+        }
 
         is >> tmp_gid;