Return Unencrypted if header is not found

Previously when drive is not in Encrypted status, bmcweb will simply
omit encryptionStatus property with Unknown returned here.
That's to say we can never reach a case where Unencrypted is populated.

We should change it to Unencrypted so when the drive is not encrypted,
Unencrypted state can be observed on BMCweb

Tested: BMCWeb have EncryptionStatus populated when drive unencrypted

Change-Id: Ie3df1df77bff40527d684f5c5b495fb2f36463e0
Signed-off-by: Hao Zhou <haoooamazing@google.com>
diff --git a/src/estoraged.cpp b/src/estoraged.cpp
index 88529b7..6c26e5a 100644
--- a/src/estoraged.cpp
+++ b/src/estoraged.cpp
@@ -380,7 +380,7 @@
     }
     catch (...)
     {
-        return Drive::DriveEncryptionState::Unknown;
+        return Drive::DriveEncryptionState::Unencrypted;
     }
 }