tests: Drop LIBVIRT_DRIVER_DIR from TESTS_ENVIRONMENT

LIBVIRT_DRIVER_DIR is defined as (what is for all intents and
purposes equivalent to) "$(abs_top_builddir)/src/.libs"; however,
as of commit bc6e2063, virDriverLoadModule() will search that
directory automatically, which means passing it through the
environment is no longer necessary.
Signed-off-by: NAndrea Bolognani <abologna@redhat.com>
Reviewed-by: NMartin Kletzander <mkletzan@redhat.com>

tests/Makefile.am

@@ -487,7 +487,6 @@ TESTS_ENVIRONMENT = \
   abs_builddir=$(abs_builddir) \
   abs_srcdir=$(abs_srcdir) \
   SHELL="$(SHELL)" \
-  LIBVIRT_DRIVER_DIR="$(lv_abs_top_builddir)/src/.libs" \
   LIBVIRT_AUTOSTART=0 \
   LC_ALL=C \
   VIR_TEST_EXPENSIVE=$(VIR_TEST_EXPENSIVE) \