Fix warnings in preparation for Rust 1.54.0

This CL fixes several new warnings generated by rustc 1.54.0.

Bug: 194812675
Test: m rust
Change-Id: I104aaf07897db4df89dd1598969dd74221bfdd0b
diff --git a/virtualizationservice/src/aidl.rs b/virtualizationservice/src/aidl.rs
index 8c5eb97..389dd23 100644
--- a/virtualizationservice/src/aidl.rs
+++ b/virtualizationservice/src/aidl.rs
@@ -658,7 +658,7 @@
     fn as_ref(&self) -> &T {
         match self {
             Self::Borrowed(b) => b,
-            Self::Owned(o) => &o,
+            Self::Owned(o) => o,
         }
     }
 }