Make piefxis import properly decode scram passwords

We encoded scramed password with base64 when exporting, but didn't apply
reverse operation on import, this adds base64 decoding on import.

This fixes issue #3167.

src/ejabberd_piefxis.erl

@@ -193,9 +193,9 @@ parse_scram_password(PassData) ->
   Split = binary:split(PassData, <<",">>, [global]),
   [StoredKeyB64, ServerKeyB64, SaltB64, IterationCountBin] = Split,
   #scram{
-    storedkey = StoredKeyB64,
-    serverkey = ServerKeyB64,
-    salt      = SaltB64,
+    storedkey = base64:decode(StoredKeyB64),
+    serverkey = base64:decode(ServerKeyB64),
+    salt      = base64:decode(SaltB64),
     iterationcount = (binary_to_integer(IterationCountBin))
   }.