process: Talloc home_trigger dummy request

Allocate the dummy request in home_trigger with talloc, instead of
allocating it on the stack, as the rest of the code expects it to be a
valid talloc context.

This fixes a talloc_abort resulting from xlat_tokenize_request invoking
talloc_typed_strdup with the dummy request as the talloc context.
Merge pull request #801 from spbnick/talloc_dummy_request

process: Talloc home_trigger dummy request