WifiNanIface: Validate interface before cleanup.

Calling invalidate() API twice would lead to fatal error. This
commit is to check if interface isValid() before doing other operations
in invalidate() API.

Bug: 166412651
Test: atest VtsHalWifiNanV1_4TargetTest WifiNanIfaceTest
Change-Id: Ia3fc48bb3d98660705bba9a32b7a5845ff7af79f
1 file changed