tests: don't fail with newer gnutls

gnutls-3.3.0 and newer leaves 2 FDs open in order to be backwards
compatible when it comes to chrooted binaries [1].  Linking
commandhelper with gnutls then leaves these two FDs open and
commandtest fails thanks to that.  This patch does not link
commandhelper with libvirt.la, but rather only the utilities making
the test pass.

Based on suggestion from Daniel [2].

[1] http://lists.gnutls.org/pipermail/gnutls-help/2014-April/003429.html
[2] https://www.redhat.com/archives/libvir-list/2014-April/msg01119.htmlSigned-off-by: NMartin Kletzander <mkletzan@redhat.com>
(cherry picked from commit 4cbc15d0)

tests/Makefile.am

@@ -645,7 +645,13 @@ commandtest_LDADD = $(LDADDS)
 
 commandhelper_SOURCES = \
 	commandhelper.c
-commandhelper_LDADD = $(LDADDS)
+commandhelper_LDADD = \
+	$(WARN_CFLAGS) \
+	$(NO_INDIRECT_LDFLAGS) \
+	$(PROBES_O) \
+	../src/libvirt_util.la \
+	$(GNULIB_LIBS)
+
 commandhelper_LDFLAGS = -static
 
 if WITH_LIBVIRTD