Fix: Malloc only when making process entry in tree

Fix: Malloc only when making process entry in tree

Description:
For some processes both FORK and EXEC events are emitted, however
we were allocating mamory in both methods, but not unallocating the
memory in failure case when entry was already present.

So we should malloc only when we are creating an entry in process tree.

Change-Id: Iedc3c10eabb41ad4da854ab8d0cf45759bbedcc7
Signed-off-by: Nishant Chaprana <n.chaprana@samsung.com>