Reduce boot verbosity.

MFC:		3 days
Remove explicit KYUAFILE=yes from tests/sys/Makefile

This causes the directory traversing Kyuafile to be installed, which in turn
causes tests/sys/pjdfstest to always be run from /usr/tests/sys

Let KYUAFILE default to auto, so the file generated by suite.test.mk gets
installed instead

MFC after: 1 week