Coverity false positive on fopen call

168        if (opts->progress_fp == NULL)

CID 1399760 (#1 of 1): Side effect in assertion (ASSERT_SIDE_EFFECT)

assignment_where_comparison_intended: Assignment opts->progress_fp = fopen(opts->progress_file_name, "w") has a side effect. This code will work differently in a non-debug build.

   	Did you intend to use a comparison ("==") instead?

169                testutil_assert((opts->progress_fp =

170                    fopen(opts->progress_file_name, "w")) != NULL);