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.

CRs-Fixed: 1043997
Change-Id: Iffd056fb29a7e16556ec9502a3d005c5bb35be50
Signed-off-by: Devi Sandeep Endluri V V <dendluri@codeaurora.org>