test: ask BusyBox its tools and recommended paths

Note: we need to add /usr/bin and /usr/sbin to the standard PATH
      for tests and the test environment itself.

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

test/test.env.in

@@ -1,6 +1,6 @@
 prefix=@prefix@
 exec_prefix=@exec_prefix@
 
-export TESTENV_PATH=/bin:/sbin:"@bindir@":"@sbindir@"
+export TESTENV_PATH=/bin:/sbin:/usr/bin:/usr/sbin:"@bindir@":"@sbindir@"
 export FINIT_CONF="@FINIT_CONF@"
 export FINIT_RCSD="@FINIT_RCSD@"