Work around bug in cargo workspaces

To me, it's intuitive that `cargo test --no-default-features`
should run the tests for all subcrates in a workspace, building
each subcrate without its default features.

In fact, this doesn't work and has never worked.  And now it's
explicitly rejected in nightly.

Tracked upstream as rust-lang/cargo#4753

.travis.yml

@@ -34,7 +34,7 @@ script:
   - ./target/release/examples/bench
 #  - ( cd trytls && ./runme )
   - ( cd bogo && ./runme )
-  - cargo build --no-default-features
-  - cargo test --no-default-features --no-run
+  - ( cd rustls && cargo build --no-default-features )
+  - ( cd rustls && cargo test --no-default-features --no-run )
   - if [[ "$COVERAGE" == "1" ]]; then ./admin/coverage          ; fi
   - if [[ "$COVERAGE" == "1" ]]; then coveralls-lcov final.info ; fi

admin/pipelines/cargo-steps.yml

@@ -9,7 +9,9 @@ steps:
     env: { "RUST_BACKTRACE": "1" }
   - script: cargo build --no-default-features
     displayName: "cargo build (debug; no default features; no run)"
+    workingDirectory: rustls
   - script: cargo test --no-default-features --no-run
     displayName: "cargo test (debug; no default features; no run)"
+    workingDirectory: rustls
   - script: cargo test --release --no-run
     displayName: "cargo test (release; no run)"