meson: fix compilation with -Dnetworkd=false, -Dkmod=no, -Dlibgcrypt=no

The tests are included under the conditional too, instead of specifying
'ENABLE_NETWORKD' in the test definition array, because libnetworkd_core
dependency is undefined if networkd is disabled.

src/test/meson.build

@@ -424,7 +424,7 @@ tests += [
    [libshared,
     libsystemd_internal],
    [libkmod],
-   '', 'manual'],
+   'HAVE_KMOD', 'manual'],
 
   [['src/test/test-ellipsize.c'],
    [libshared],