net: qrtr: Send HELLO message on endpoint register

Hello message is currently sent in response to a hello message received
by the ns. When two procs operate in this slave model, then neither of
them exchange the Hello message. This will halt further communication
from happening. Update QRTR to send a hello message once a new endpoint
is registered.

Prevent duplicate Hello messages from reaching the NS because NS will
echo the packet back. On two systems running QRTR, this will loopback
infinitely.

Change-Id: Id8483341717ed3075b426b142b21e018cefbd580
Signed-off-by: Chris Lew <clew@codeaurora.org>