[4239] MySQL unit tests in dhcpsrv now use production db create script

[4239] MySQL unit tests in dhcpsrv now use production db create script

src/lib/dhcpsrv/tests/mysql_lease_mgr_unittest.cc
    TEST(MySqlOpenTest, OpenDatabase) - pass in show_err=true for call
    to createMySQLSchema()

src/lib/dhcpsrv/testutils/Makefile.am
    - Added definition of TEST_ADMIN_SCRIPTS_DIR
    - removed schema_mysql_copy.h

src/lib/dhcpsrv/testutils/mysql_schema.cc
    - Removed include of schema_mysql_copy.h
    - destroyMySQLSchema() - now contains destroy_statment[] formerly
    defined in schema_mysql_copy.h
    - createMySQLSchema() - Creates the database through command line
    invocation of MySQL cli, mysql, passing it the production database
    creation script