Attempt to fix EPEL8 build

Use --without-gnutls-version-check; as if EPEL8 *does* get the fix for
the zero-client-random bug it will probably come without a version bump.

This also partially reverts commit 68641c0 which disabled the use of
--with-default-gnutls-priority on *all* EPEL versions, but since I wasn't
building for EPEL8 at that point I don't think it was done for EPEL8
specifically, and can probably be restored.

Signed-off-by: David Woodhouse <dwmw2@infradead.org>

openconnect.spec.in

@@ -116,7 +116,7 @@ fi
 %configure	--with-vpnc-script=/etc/vpnc/vpnc-script \
 		--disable-dsa-tests \
 %if %{use_gnutls}
-%if 0%{?fedora} || 0%{?rhel} > 8
+%if 0%{?fedora} || 0%{?rhel} > 7
 		--with-default-gnutls-priority="@OPENCONNECT,SYSTEM" \
 		--without-gnutls-version-check \
 %endif