firmware_handler: allow committing repeatedly

Committing repeatedly while a commit is in progress has no effect and
just returns success to the caller.  Previous behavior was to fail.

Signed-off-by: Patrick Venture <venture@google.com>
Change-Id: Ie237d68f661e7f0a93700724a512e1d9965663a1
diff --git a/firmware_handler.cpp b/firmware_handler.cpp
index 8c9ad43..c7164dc 100644
--- a/firmware_handler.cpp
+++ b/firmware_handler.cpp
@@ -538,10 +538,10 @@
         return false;
     }
 
-    /* Can only be called once per verification. */
+    /* Calling repeatedly has no effect within an update process. */
     if (state == UpdateState::verificationStarted)
     {
-        return false;
+        return true;
     }
 
     /* Set state to committing. */