Assorted refactoring

Mostly removing duplication. Also added a comment as suggested by
Andrew.

Bug: 161471326
Test: composd_cmd async-odrefresh

Change-Id: I7da83cb825de7b4fd2267b1e496808a423544c16
diff --git a/compos/composd/src/odrefresh_task.rs b/compos/composd/src/odrefresh_task.rs
index b7de479..56b697e 100644
--- a/compos/composd/src/odrefresh_task.rs
+++ b/compos/composd/src/odrefresh_task.rs
@@ -22,7 +22,7 @@
     ICompilationTask::ICompilationTask, ICompilationTaskCallback::ICompilationTaskCallback,
 };
 use android_system_composd::binder::{Interface, Result as BinderResult, Strong};
-use anyhow::{bail, Context, Result};
+use anyhow::{Context, Result};
 use compos_aidl_interface::aidl::com::android::compos::ICompOsService::ICompOsService;
 use compos_common::odrefresh::ExitCode;
 use log::{error, warn};
@@ -140,11 +140,7 @@
     )?;
 
     drop(fd_server_raii);
-    if let Some(exit_code) = ExitCode::from_i32(exit_code.into()) {
-        Ok(exit_code)
-    } else {
-        bail!("odrefresh exited with {}", exit_code)
-    }
+    ExitCode::from_i32(exit_code.into())
 }
 
 /// Returns an owned FD of the directory. It currently returns a `File` as a FD owner, but