replace left quantum string for enable_lb

writing the correct config for horizon to show LBaaS entry properly
like:

OPENSTACK_NEUTRON_NETWORK = {
    'enable_lb': True
}

Change-Id: I7f522a150a3732ee734f2b818910ff92c8c73028
Fixes: bug #1200098
Merge "replace left quantum string for enable_lb"