Simplify the serialize_config test

Setting up the Package struct in this test was necessary just to have
things to compile, otherwise nothing from the struct was used at
all. With the TestPkg struct in place, we don't need to do the setup
anymore.

Signed-off-by: Krzesimir Nowak <krzesimir@kinvolk.io>

components/sup/src/manager/service/config.rs

@@ -467,8 +467,6 @@ mod test {
     use toml;
     use tempdir::TempDir;
 
-    use hcore::package::{PackageIdent, PackageInstall};
-
     use super::*;
     use error::Error;
 
@@ -763,20 +761,14 @@ mod test {
 
     #[test]
     fn serialize_config() {
-        let pkg_id = PackageIdent::new("testing", "testing", Some("1.0.0"), Some("20170712000000"));
-        let pkg_install = PackageInstall::new_from_parts(
-            pkg_id.clone(),
-            PathBuf::from("/tmp"),
-            PathBuf::from("/tmp"),
-            PathBuf::from("/tmp"),
-        );
-        let pkg = Pkg::from_install(pkg_install).expect("Could not create package!");
         let concrete_path = TempDir::new("habitat_config_test").expect("create temp dir");
-
-        let mut cfg = Cfg::new(&pkg, Some(&concrete_path.as_ref().to_path_buf()))
-            .expect("Could not create config");
-
-        let default_toml = "shards = []\n\n[datastore]\ndatabase = \"builder_originsrv\"\npassword = \"\"\nuser = \"hab\"\n";
+        let pkg = TestPkg::new(&concrete_path);
+        let mut cfg = Cfg::new(&pkg, None).expect("Could not create config");
+        let default_toml = "shards = []\n\n\
+                            [datastore]\n\
+                            database = \"builder_originsrv\"\n\
+                            password = \"\"\n\
+                            user = \"hab\"\n";
 
         cfg.default = Some(toml::Value::Table(
             toml::de::from_str(default_toml).unwrap(),