diag: Fix data corruption.

Diag uses krealloc for allocating memory if number of client exceeds 15 as
krealloc doesn't initialize memory to 0 resulting in corruption of data.
This fix initializes the memory after allocation.

CRs-Fixed: 347675
Change-Id: Ide504a18adc2e1fc282c5543ec77818f346e4015
Signed-off-by: Ashay Jaiswal <ashayj@codeaurora.org>