Applies the existing client_data->is_translating debug flag to avoid a curiosity and an assert on translation failure stemming from client use of dr_app_pc_from_cache_pc() on a sampling itimer.
Augments the client.timer test to run with -disable_traces and use a lot of indirect branches to trigger a curiosity on xl8 failure on every run when the iterations are increased (a little too high for our small regression tests though). With this fix, the curiosity never occurs.
Issue: #4669