test70: reduce ITERATIONS

	. full number was needed to reliably trigger the race
	  condition
	. takes a bit too long (7 mins on fast x86 hardware) for a
	  condition that "can't" happen again, so let's cut the iteration
	  count and trust that the test will trigger soon enough for
	  a similar condition in the future.

Change-Id: I2d38b87c25327adbbff91b7db6191648aa1dd8fd