loader: Remove ignore config to run bzImage loader unit test

ignore has not taken effect to avoid run bzImage loader unit
test, remove it. It's required to follow steps on README.md
to do the test.

Signed-off-by: Cathy Zhang <cathy.zhang@intel.com>

Author: bjzhjing

README.md

@@ -87,7 +87,7 @@ than the coverage reported in [tests/coverage](tests/coverage).
 
 As we don't want to distribute an entire kernel bzImage, the `load_bzImage` test is ignored by
 default. In order to test the bzImage support, one needs to locally build a bzImage, copy it
-to the `src/loader` directory and run the ignored test:
+to the `src/loader` directory and run cargo test:
 
 ```shell
 # Assuming your linux-loader and linux-stable are both under $LINUX_LOADER
@@ -101,5 +101,5 @@ $ docker run -it \
            --volume $(pwd):/linux-loader \
            fandree/rust-vmm-dev
 $ cd linux-loader/
-$ cargo test -- --ignored
+$ cargo test 
 ```

src/loader/mod.rs

@@ -391,7 +391,6 @@ mod test {
     #[allow(safe_packed_borrows)]
     #[allow(non_snake_case)]
     #[test]
-    #[ignore]
     fn load_bzImage() {
         let gm = create_guest_mem();
         let image = make_bzImage();