Touch process watchdog in built-in precision tests

Computing reference intervals in built-in precision tests can take a
long time, especially on platforms where toggling floating-point
rounding mode is costly. Workaround is to periodically touch test
process watchdog to give more time for the computation to complete.

Bug: 26629688

Change-Id: I529bc77e638fc75cd0c152bb761775ad260772be
1 file changed