No throw when backfillKeys fails (#498)

Author: clarkxuyang

src/main/java/com/uid2/admin/cloudencryption/CloudEncryptionKeyManager.java

@@ -72,7 +72,6 @@ public void backfillKeys() throws Exception {
             LOGGER.info("Key backfill complete. Diff: {}", diff);
         } catch (Exception e) {
             LOGGER.error("Key backfill failed", e);
-            throw e;
         }
     }