Per EPP RFC 5730, the <clTRID> element is optional. However, we weren't handling
it not being specified in asynchronous contact/host deletions because we were
adding it directly as a parameter value on a task, which does not allow null and
thus threw a NullPointerException.
This fixes handling for nulls (the parameter isn't set at all) and adds a test.
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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=194123259