LE: Disable L2CAP connection parameter update during pairing

Some peripherals change the connection parameters during the pairing
procedure. Ideally when service discovery is started, connection
parameters are reset to default values. In instances where the
connection update fails, service discovery takes a very long time and
may result in a GATT application not receiving a connection status
update.
Disabling connection paramter update during service discovery ensures
a quick service discovery and improves interoperability.

Bug: 8714594
Change-Id: I2177e57bf250b99e314a1b020cd0fadbd480214e