i965: Move mistakenly placed line

Ken called this out in review, but it seems I forgot to make the change.
I noticed that the control flow annotations in the fragment shader
disassembly of tests/shaders/glsl-fs-loop-continue.shader_test were not
correct, and moving this line to the correct place fixes it.

src/intel/compiler/brw_disasm_info.c

@@ -123,8 +123,8 @@ disasm_annotate(struct disasm_info *disasm,
    struct inst_group *group;
    if (!disasm->use_tail) {
       group = disasm_new_inst_group(disasm, offset);
-      disasm->use_tail = false;
    } else {
+      disasm->use_tail = false;
       group = exec_node_data(struct inst_group,
                              exec_list_get_tail_raw(&disasm->group_list), link);
    }