Fix GString memory leak in read_stream function

The 'stream' GString was not freed before returning from read_stream()
in two places:
1. When kill_recv is TRUE at the start of the loop
2. At the end of the function after the loop exits

Added g_string_free(stream, TRUE) before both return statements.

src/server/server.c

@@ -109,6 +109,7 @@ read_stream(void)
     while (TRUE) {
         if (kill_recv) {
             _shutdown();
+            g_string_free(stream, TRUE);
             return 0;
         }
 
@@ -167,6 +168,7 @@ read_stream(void)
         memset(buf, 0, sizeof(buf));
     }
 
+    g_string_free(stream, TRUE);
     return 0;
 }