DSLX: IR converter attempts to convert test procs?

Get the following error when running the GCM GHASH test (in flight; will be submitted soon) DSLX interpreter *without the --compare=none* flag:

```
xls/modules/aes/aes_128_ghash.x:334:26-334:41
0332: [u8:0x9e, u8:0x5e, u8:0x57, u8:0x14],
0333: ];
0334: let _ = assert_eq(tag, expected);
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^-------------^ ConversionError: Could not find name for invocation: assert_eq; available: [block_to_u128, u128_to_block, gf128_mul, xor_block, get_current_state, aes_128_ghash.config, aes_128_ghash.next, aes_128_ghash_test.config, aes_128_ghash_test.next]
0335:
0336: // Test 2: two AAD blocks, three ctxt blocks. Random data.
```

Looks like it's trying to IR-convert the test?