meson: switch code dependency to libsystemd

For a while now systemd has packaged a separate `libsystemd`.  For
meson dependency, `systemd` should be used when looking for systemd
service file paths and `libsystemd` should be used for `sd_*` functions.

Update the dependency accordingly.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I9768dd66c4180085f201a0b77385d696bdd1680f
diff --git a/test/meson.build b/test/meson.build
index 607c873..607e2a0 100644
--- a/test/meson.build
+++ b/test/meson.build
@@ -59,7 +59,15 @@
     build_by_default: false,
     override_options: ['b_lundef=true'],
     implicit_include_directories: false,
-    dependencies: [boost, phosphor_logging_dep, crypto, systemd, sdbusplus_dep, gtest, gmock]
+    dependencies: [
+        boost,
+        crypto,
+        gmock,
+        gtest,
+        libsystemd_dep,
+        phosphor_logging_dep,
+        sdbusplus_dep,
+    ]
   ))
 
 # Build/add closesession_unittest to test suite