MAP: Remove extra line feed in Message Listing object

Usecase:
1) Establish MAP session.
2) Do Message Listing for any folder with messages.

Issue:
Extra line feed is present and seen in messageListing xml object
as 
 for carkit other than BENZ which causes parsing issues
in some carkits.

Root Cause:
FastXmlSerializer.startDocument() and xmlMsgElement.text("\n")
both add line feed.

Fix:
Line feed is already added method FastXmlSerializer.startDocument()
So need to remove extra line feed added.

Test: No extra junk characters are seen in Mesage Listing Response

Fixes: 77447850
Change-Id: I86a7bff088982fe4906399f645a28f03b8073d83