Re-enable BLAS backend tests (#234)

* Make blas tests work again with linfa 0.7.1

* Re-enable CI test with blas feature

* Pin cargo lock version 3

Author: relf

.github/workflows/test.yml

@@ -76,6 +76,6 @@ jobs:
         uses: actions-rs/cargo@v1
         with:
           command: test
-          args: --all --release --features persistent-moe,nlopt # ,blas,linfa/intel-mkl-static   # disabled till linfa 0.8 
+          args: --all --release --features persistent-moe,nlopt,blas,linfa/intel-mkl-static