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: Iaf69a4f17cb677d1d34558f4aab33e0e20ae4868
Signed-off-by: Nishant Chaprana <n.chaprana@samsung.com>