Remove redundant GATT_StartIf

GATT_StartIf is just sending connect callback about all currently
connected devices, even ones that this app is not interested in.

For btif/java apps, we will trigger connection attempt to just one
device right after registration, which would trigger connect callback
anyway.

For all bta layer apps, they do guard inside connect callback to make
sure code is triggered for already known device, but the devices are
considered as known only after they already connected, and some event
triggered app to create control block.

Thus, GATT_StartIf is surplus feature that should be removed.

Test: run all sl4a GATT tests
Change-Id: I8c45b92dbbf80894c32bb870eb392e766063c934