tools/osbuild-depsolve-dnf: extend default config with loaded

Instead of completely overriding the default solver configuration with
the one loaded from a file, just extend the default config. This will
allow to specify just desired config options and keeping the defaults
for the rest.

Signed-off-by: Tomáš Hozza <thozza@redhat.com>

tools/osbuild-depsolve-dnf

@@ -20,7 +20,8 @@ config = {"use_dnf5": False}
 config_path = os.environ.get("OSBUILD_SOLVER_CONFIG") or "/usr/lib/osbuild/solver.json"
 try:
     with open(config_path, encoding="utf-8") as f:
-        config = json.load(f)
+        loaded_config = json.load(f)
+        config.update(loaded_config)
 except FileNotFoundError:
     pass