iso-tester: always use DEFER_SETUP for multiple CIS in same CIG

iso-tester: always use DEFER_SETUP for multiple CIS in same CIG

There is a race between multiple connect() for CIS in the same CIG.
connect() will both reconfigure the CIG and connect the CIS, but CIG
cannot be reconfigured once one CIS has already connected.  That these
tests pass currently relies on some timing/event ordering in the
emulator.

Connecting multiple CIS in same CIG is meant to be done using
DEFER_SETUP, so change the tests to use it, so we test the intended
usage.