Creating the unicast group before both ISO connections have been configured might cause issue

[rick1082]

Describe the bug
I try to modify the unicast_audio_client and unicast_audio_server for creating TWS scenario demo (one client connects to two servers).
And if the unicast group is created before both ISO connections have been configured, then the CIG creating parameter will be wrong.

I'm using controller from here with the application in https://github.com/rick1082/zephyr/tree/multilink_audio

And running the on nRF5340-DK.

To Reproduce
Steps to reproduce the behavior:

1. Checkout the unicast_audio_client from above branch and program to one nRF5340-DK as client
2. Checkout the unicast_audio_server from above branch, and program to nRF5340-DK as left headset server
3. Checkout the unicast_audio_server from above branch, remove following line and program to nRF5340-DK as right headset server
   https://github.com/rick1082/zephyr/blob/multilink_audio/samples/bluetooth/unicast_audio_server/src/main.c#L60
4. Program all the DKs with ble5-ctr-rpmsg_3247.hex on the network core
5. Turn on both of servers, and then turn on the client
6. Then we see the client shows following log

[00:00:10.104,827] bt_hci_core: opcode 0x2064 status 0x0c
[00:00:10.104,858] bt_iso: bt_iso_chan_connect: Failed to connect CISes: -5
[00:00:10.104,858] bt_unicast_client: bt_audio_stream_connect: -5

7. And in the HCI traffic log, it shows following log indicated the CIG only created with one CIS

< HCI Command: LE Set Connected I.. (0x08|0x0062) plen 24 #185 [hci0] 5.555816
CIG ID: 0x00
Master to Slave SDU Interval: 10000 us (0x002710)
Slave to Master SDU Interval: 10000 us (0x002710)
SCA: 201 - 500 ppm (0x00)
Packing: Sequential (0x00)
Framing: Unframed (0x00)
Master to Slave Maximum Latency: 10 ms (0x000a)
Slave to Master Maximum Latency: 10 ms (0x000a)
Number of CIS: 1
CIS ID: 0x00
Master to Slave Maximum SDU Size: 40
Slave to Master Maximum SDU Size: 0
Master to Slave PHY: LE 2M (0x02)
Slave to Master PHY: LE 2M (0x02)
Master to Slave Retransmission attempts: 0x02
Slave to Master Retransmission attempts: 0x00
HCI Event: Command Complete (0x0e) plen 8 #186 [hci0] 5.559716
LE Set Connected Isochronous Group Parameters (0x08|0x0062) ncmd 1
Status: Success (0x00)
CIG ID: 0x00
Number of Handles: 1
Connection Handle: 2

Expected behavior
The bt_audio API should work for creating the unicast group before both ISO connections been configured.

Logs and console output
The btmon format HCI log from client as following:
client_hci.log
The application log from client as following
client_application.log

[github-actions]

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