Mms: Fix phone cannot add contacts information to message.

In onStart function, loadMessagesAndDraft will be executed late,
then mTextEditor text not set to WorkingMessage text which
causes phone cannot add contacts information to message issue.

In onStart function we get WorkingMessage text first. We will
update mTextEditor text if the WorkingMessage text is not null.

CRs-Fixed: 500801

Change-Id: I927a57ee35bda5d39402473fdc0964e923bfa55e