Bluetooth: Mesh: shell: Fix AppKey Add command handler
Bluetooth: Mesh: shell: Fix AppKey Add command handler

The command handler already has support for decoding from hex, however
it was not using the decoded value when calling the client API.

Signed-off-by: Johan Hedberg <628991c7b0a19c384f9b99c21ec330ce952bb838@intel.com>

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