runtimtest: fix validatePosixMounts
runtimtest: fix validatePosixMounts

Commit 20a71e45 implemented a number of improvements, including a
modification to validatePosixMounts, which results in the following
linter warning:

> cmd/runtimetest/main.go:1179:4: SA4006: this value of `rfcError` is never used (staticcheck)
> 			rfcError, err = c.Ok(false, specerror.MountsInOrder, spec.Version, fmt.Sprintf("mounts[%d] (%s) found", i, configMount.Destination))
>			^

It seems that c.harness.YAML() call was mistakenly placed into the
"else" code block. Move it out.

Signed-off-by: Kir Kolyshkin <3a017b8ddb3f9cf3e4a59978b004111bdeb97f08@gmail.com>

opencontainers/runtime-tools,opencontainers/runtime-tools