[3080] Use the correct header name schema_mysql_copy.h in MySQL unit test.

src/lib/dhcpsrv/tests/mysql_lease_mgr_unittest.cc

@@ -38,7 +38,7 @@ using namespace std;
 namespace {
 
 // This holds statements to create and destroy the schema.
-#include "schema_copy.h"
+#include "schema_mysql_copy.h"
 
 // Connection strings.
 // Database: keatest