qcacld-3.0: Send install key command response for open mode connection

Currently for Open mode, the install key command is not allowed
but usually set key with 0 length is sent in open mode and in
set key response path the OBSS scan is configured to firmware.

So send dummy response for install key command to go for open
mode connection.

Change-Id: Ia3665ca018114bbf354b8c3138a7c4d81f7f9707
CRs-Fixed: 2769414