defconfig: Enabling config INET_DIAG_DESTROY

Sockets that are opened before VPN is connected
are supposed to be destroyed once it is connected.
VPN related CTS testcases are failing without the
ability to destroy sockets. Enabling INET_DIAG_DESTROY
to fix these testcases.

Change-Id: Iad01cb10faa892897f180ad217b27a56c2da89b5
Signed-off-by: Ashwanth Goli <ashwanth@codeaurora.org>