Prevent undeclared public network access

Stop a few tests which aren't marked with `public_network_test` from
trying to access crates.io.

Author: sebastianpoeplau

tests/testsuite/cargo_add/normalize_name_path_existing/mod.rs

@@ -7,6 +7,9 @@ use cargo_test_support::Project;
 
 #[cargo_test]
 fn case() {
+    // Prevent network access by initializing the dummy registry.
+    cargo_test_support::registry::init();
+
     let project = Project::from_template(current_dir!().join("in"));
     let project_root = project.root();
     let cwd = &project_root;

tests/testsuite/cargo_add/normalize_name_path_existing/stderr.term.svg

@@ -4,6 +4,9 @@ use cargo_test_support::{current_dir, file};
 
 #[cargo_test]
 fn case() {
+    // Prevent network access by initializing the dummy registry.
+    cargo_test_support::registry::init();
+
     let _ = RegistryBuilder::new()
         .alternative()
         .no_configure_token()

tests/testsuite/cargo_info/within_ws_with_alternative_registry/mod.rs

@@ -6065,6 +6065,9 @@ src/main.rs
 
 #[cargo_test]
 fn workspace_with_local_deps_index_mismatch() {
+    // Prevent network access by initializing the dummy registry.
+    registry::init();
+
     let alt_reg = registry::RegistryBuilder::new()
         .http_api()
         .http_index()
@@ -6123,12 +6126,12 @@ fn workspace_with_local_deps_index_mismatch() {
 [PACKAGING] level2 v0.0.1 ([ROOT]/foo/level2)
 [PACKAGED] 4 files, [FILE_SIZE]B ([FILE_SIZE]B compressed)
 [PACKAGING] level1 v0.0.1 ([ROOT]/foo/level1)
-[UPDATING] crates.io index
+[UPDATING] `dummy-registry` index
 [ERROR] failed to prepare local package for uploading
 
 Caused by:
   no matching package named `level2` found
-  location searched: crates.io index
+  location searched: `dummy-registry` index (which is replacing registry `crates-io`)
   required by package `level1 v0.0.1 ([ROOT]/foo/level1)`
 
 "#]])