Bluetooth: Remove HCI_PI_MGMT_INIT flag for sockets

This flag is of no use right now and is in fact harmful in that it
prevents the HCI_MGMT flag to be set for any controllers that may need
it after the first one that bluetoothd takes into use (the flag is
cleared for the first controller so any subsequent ones through the same
bluetoothd mgmt socket never get the HCI_MGMT flag set).

Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
Acked-by: Marcel Holtmann <marcel@holtmann.org>