pcu: TC_cs_max_dl: Fix race condition waiting for first DL data after X2002

Since recently osmo-pcu arms the X2002 in a more fitting place (later,
when paging.cnf is received from osmo-bts over PCUIF).
Since we use same X2002 value in TTCN3 to wait for the timer to trigger,
in the past it was always fine (the X2002 at osmo-pcu always already had
triggered before the one in ttcn3 after receiving the ImmAss).

However, now the timer is roughly set at the same time in both places (ttcn3 and
osmo-pcu) and hence there may be race conditions where we request a
DL data block before the X2002 triggered at osmo-pcu, in which case we
receive a DL dummy block because the TBF is not yet in the FLOW state.

Change-Id: If7121473a3580b40d3a658dc38b9bb1421196127
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M pcu/PCU_Tests.ttcn
1 file changed, 17 insertions(+), 2 deletions(-)