Initialize MD5 in logging in background

Use a background task to call MessageDigest.getInstance in order to
avoid a possible disk read on initialization.

Bug: 26069217
Change-Id: I0091ce012bcd811dfca0e85c21a12c54913ed919
diff --git a/telecomm/java/android/telecom/TelecomManager.java b/telecomm/java/android/telecom/TelecomManager.java
index f1cbb9a..9f478df 100644
--- a/telecomm/java/android/telecom/TelecomManager.java
+++ b/telecomm/java/android/telecom/TelecomManager.java
@@ -498,6 +498,7 @@
             mContext = context;
         }
         mTelecomServiceOverride = telecomServiceImpl;
+        android.telecom.Log.initMd5Sum();
     }
 
     /**