AppVeyor: use --manifest-path over --package in tests

--package causes problems where multiple versions exist
(an issue since rdrand depends on rand_core:0.3).
Also, we definitely don't need both.

appveyor.yml

@@ -37,13 +37,6 @@ test_script:
   - cargo test --features=serde1,log
   - cargo test --benches --features=nightly
   - cargo test --examples
-  - cargo test --package rand_core
-  - cargo test --package rand_core --no-default-features --features=alloc
-  - cargo test --package rand_isaac --features=serde1
-  - cargo test --package rand_xorshift --features=serde1
-  - cargo test --package rand_xoshiro
-  - cargo test --package rand_chacha
-  - cargo test --package rand_hc
   - cargo test --manifest-path rand_core/Cargo.toml
   - cargo test --manifest-path rand_core/Cargo.toml --no-default-features --features=alloc
   - cargo test --manifest-path rand_isaac/Cargo.toml --features=serde1