btm: btm_iso: Fix handling cancelled Create CIS procedure

This fixes kIsoEventCisDisconnected event that was not generated
when the CIS creation has been cancelled by local host.

As per Core 5.4 Vol 4, Part E, 7.1.6 Disconnect Command:
"If this command is issued for a CIS on the Central and the CIS
is successfully terminated before being established, then an
HCI_LE_CIS_Established event shall also be sent for this CIS with
the Status Operation Cancelled by Host (0x44)."

Bug: 357472821
Flag: Exempt; regression covered by unit test added
Test: atest net_test_btm_iso
Change-Id: I7512e5ff26f40ef4f58f0b7f1473ba07170a7582