client-server conversation arch for async scan

client-server conversation arch for async scan

Async operation process

AS-IS
1) getting scannable file list from server
2) dispatch scan file operation per item in list

TO-BE
1) dispatch async scanning with files/dirs list by client
2) Client receives event only when malware detected by server
   unless file scanned callback is registered.

IPC time is much more lower than before because IPC isn't needed
for file scanned without malware when callback isn't registered.

Memory usage on client side is much less than before because client
doesn't receive a bunch of scannable file list.
Client only receives event when callback call needed or operation completed.

Change-Id: I0c913a2fbdf75c2abe99cdf6d757fdb0f264145d
Signed-off-by: Kyungwook Tak <k.tak@samsung.com>