Bluetooth: Enter active mode before establishing a SCO link.

Bluetooth: Enter active mode before establishing a SCO link.

When in sniff mode with a long interval time (1.28s) it can take 4+ seconds to
establish a SCO link. Fix by requesting active mode before requesting SCO
connection. This improves SCO setup time to ~500ms.

Bluetooth headsets that use a long interval time, and exhibit the long SCO
connection time include Motorola H790, HX1 and H17. They have a CSR 2.1 chipset

Verified this behavior and fix with host Bluetooth chipsets: BCM4329 and
TI1271.

Signed-off-by: Nick Pelly <npelly@google.com>