tests: move some files to the tests package

some test support libraries had escaped confinement and were found
wandering around the utilities package:

	/usr/tests/lib/csu/dynamiclib/libh_csu.so
	/usr/tests/lib/libthr/dlopen/h_pthread_dlopen.so
	/usr/tests/lib/libthr/dlopen/h_pthread_dlopen.so.1
	/usr/tests/sys/vm/stack/libsoxstack.so

these aren't built using bsd.test.mk, so they don't get the default
PACKAGE=tests option; set this by hand in their Makefiles to put them
back where they belong.

Reviewed by:	manu, des, emaste
Approved by:	des (mentor)
Differential Revision:	https://reviews.freebsd.org/D50147

lib/csu/tests/dso/Makefile

@@ -1,4 +1,6 @@
 .PATH: ${.CURDIR:H}
+
+PACKAGE=	tests
 SHLIB=		h_csu
 SHLIB_NAME=	libh_csu.so
 SHLIB_MAJOR=	1

lib/libthr/tests/dlopen/dso/Makefile

@@ -1,6 +1,7 @@
 TESTSRC=	${SRCTOP}/contrib/netbsd-tests/lib/libpthread/dlopen/dso
 WARNS?=		3
 
+PACKAGE=	tests
 SHLIB=		h_pthread_dlopen
 SHLIB_MAJOR=    1
 SHLIB_NAME=	h_pthread_dlopen.so.${SHLIB_MAJOR}

tests/sys/vm/soxstack/Makefile

@@ -1,3 +1,4 @@
+PACKAGE=	tests
 SHLIB=		soxstack
 SHLIB_NAME=	libsoxstack.so
 SHLIB_MAJOR=	1