Don't hash for the cache if it's disabled (#2816)

This fixes an issue where even if the wasmtime cache was disabled we're
still calculating the sha256 of modules for the hash key. This hash
was then simply discarded if the cache was disabled!

crates/cache/src/lib.rs

@@ -48,17 +48,17 @@ impl<'config> ModuleCacheEntry<'config> {
         T: Hash,
         U: Serialize + for<'a> Deserialize<'a>,
     {
+        let inner = match &self.0 {
+            Some(inner) => inner,
+            None => return compute(state),
+        };
+
         let mut hasher = Sha256Hasher(Sha256::new());
         state.hash(&mut hasher);
         let hash: [u8; 32] = hasher.0.finalize().into();
         // standard encoding uses '/' which can't be used for filename
         let hash = base64::encode_config(&hash, base64::URL_SAFE_NO_PAD);
 
-        let inner = match &self.0 {
-            Some(inner) => inner,
-            None => return compute(state),
-        };
-
         if let Some(cached_val) = inner.get_data(&hash) {
             let mod_cache_path = inner.root_path.join(&hash);
             inner.cache_config.on_cache_get_async(&mod_cache_path); // call on success