We are trying to set up a CI environment, using the Migration tool, to effectively test a deployment to production, using the sandbox environment.  We are looking to run all of the tests that would be run in production, so we can catch any issues in the coding, or deployment process itself, before we try to push it to production.

The problem we are running into is that the deployment is failing on tests from installed packages

Example:

Test failure, method: al.DatabaseUtilsTest.test_query_ListString -- System.DmlException: Insert failed. First exception on row 0; first error: FIELD_CUSTOM_VALIDATION_EXCEPTION, You must at least input postal code for this site location: [] stack (al)
External entry point

All of our test successfully pass and we have >75% test coverage.

Migration Target:

<target name="deployTest">
	<sf:deploy username="${sf.username}" password="${sf.password}" runAllTests="True" serverurl="${sf.serverurl}" deployRoot="src" />
</target>

I have been poring over the Migration Tool Guide for a couple of days, but I am not finding any way to address this.  The guide says that in a deployment "to a production organization, all the tests in your organization, except for those that originate from installed managed packages, are automatically run." (emphasis added) 

Should I take my results to mean that in the sandbox, installed packages are tested too?

Is there some way of eliminating installed package tests from 'runAllTests="True"'?