MINOR: http-conv: Remove unreachable goto statement in sample_conv_q_preferred

This was reported by Coverity. In sample_conv_q_preferred() function, a goto
statement after a "while(1)" loop is unreachable. Instead of just removing
it, the same goto statement in the loop is replaced by a break. It is safer
this way, in case the loop change in future.

This patch should fix the issue #2683.

src/http_conv.c

@@ -157,7 +157,7 @@ static int sample_conv_q_preferred(const struct arg *args, struct sample *smp, v
 				if (http_language_range_match(token, toklen, w, str - w))
 					goto look_for_q;
 				if (*str == '\0')
-					goto expect_comma;
+					break;
 				w = str + 1;
 			}
 			str++;