Fixing neutron-mlnx-agent service crash bug

Incorrect permissions for mlnx_conf.ini made the service crash.
The fix sets the owner as 'neutron' since the service is being run as neutron user.

Closes-bug: #1390185
Change-Id: Ieb0927d644c5a1d7eead12a32580f88d4d790e43
Signed-off-by: Gil Meir <gilmeir@mellanox.com>
Merge "Fixing neutron-mlnx-agent service crash bug"