tests: Bluetooth: CAP: Fix issues for CAP BSIM tests

Some CAP BSIM could not be built after some commits were merged.
One CAP test was missing a call to backchannel_sync_send_all
A change in the controller and/or timing seems to have triggered
an old issue on a bunch of tests. Theses tests have been disabled
while the issue is pending investigation.

Signed-off-by: Emil Gydesen <emil.gydesen@nordicsemi.no>