MFC r289172,r290254:

r289172:

Refactor the test/ Makefiles after recent changes to bsd.test.mk (r289158) and
netbsd-tests.test.mk (r289151)

- Eliminate explicit OBJTOP/SRCTOP setting
- Convert all ad hoc NetBSD test integration over to netbsd-tests.test.mk
- Remove unnecessary TESTSDIR setting
- Use SRCTOP where possible for clarity

r290254:

Remove unused variable (SRCDIR)

MFC r269977

Skip pgrep-j and pkill-j if jail or jls is not installed.

Even though jail is part of the base system, it can be disabled by src.conf
settings. Therefore, it should be listed as a required program for tests that
use it.

MFC r269977

Skip pgrep-j and pkill-j if jail or jls is not installed.

Even though jail is part of the base system, it can be disabled by src.conf
settings. Therefore, it should be listed as a required program for tests that
use it.