diag: DCI Multi-Client Crash Fix & Cummulative Log and Event Mask Fix

Clearing the DCI Log and Event Masks did not change the cummulative
masks properly. This fix updates the masks whenever there is a change
in the log and event masks. Also, this fixes a NULL pointer issue
when there is more than one DCI Client

Change-Id: Ia92751ffb7a12b65fd81725257746d732804d6ae
Signed-off-by: Ravi Aravamudhan <aravamud@codeaurora.org>