tree: fix tls key mem leak

Valgrind revealed a mem leak when specifying the tls key through
both the config JSON file and the CLI. This was because memory
allocated through strdup via the nvme_get_ctrl_attr() while
fetching the tls key was not getting freed. Fix it.

Signed-off-by: Martin George <[email protected]>

src/nvme/tree.c

@@ -1887,7 +1887,9 @@ static int nvme_configure_ctrl(nvme_root_t r, nvme_ctrl_t c, const char *path,
 			       const char *name)
 {
 	DIR *d;
-	char *host_key, *ctrl_key, *tls_psk;
+	char *host_key, *ctrl_key;
+
+	_cleanup_free_ char *tls_psk = NULL;
 
 	d = opendir(path);
 	if (!d) {