Fix associations being defined before templat is written

MSP-9228

Mdm::Module::Instance associations were not defined prior to writing the
template because the after(:build) for metasploit-model, which wrote the
template, ran before the after(:build) for metasploit_data_models because
trait callbacks run before base callbacks.  This has been worked around
by the after(:build) in metasploit-model 0.21.1 adding a
before_write_template callback to the ignored attributes, which this
commit now uses.