main: preserve config::client_encryption_options configuration source

With dynamically updateable configuration, tracking the source of a value
is more important, since we'll accept or reject updates depending on the source.

Fix the source of client_encryption_options, which we RMW, by preserving the original
source.

main.cc

@@ -521,7 +521,7 @@ int main(int ac, char** av) {
             } else {
                 ceo["enabled"] = "false";
             }
-            cfg->client_encryption_options(ceo);
+            cfg->client_encryption_options(std::move(ceo), cfg->client_encryption_options.source());
 
             using namespace locator;
             // Re-apply strict-dma after we've read the config file, this time