Fix assertion failure when using -X and lock-file in configuration

Fix assertion failure when using -X and lock-file in configuration

When 'lock-file <lockfile1>' was used in configuration at the same time
as using `-X <lockfile2>` in `named` invocation, there was an invalid
logic that would lead to a double isc_mem_strdup() call on the
<lockfile2> value.

Skip the second allocation if `lock-file` is being used in
configuration, so the <lockfile2> is used only single time.

(cherry picked from commit 4f68def5e966f0d359833b64837e25f0cb60fb6a)