Fix: sessiond: event, filter expression, bytecode, exclusions might leak

Reported by Coverity:

    CID 1475803: Resource leak (RESOURCE_LEAK)
    Variable filter_expression going out of scope leaks the storage it points to.

    CID 1475816: Resource leak (RESOURCE_LEAK)
    Variable exclusions going out of scope leaks the storage it points to.

    CID 1475817: Resource leak (RESOURCE_LEAK)
    Variable bytecode going out of scope leaks the storage it points to.

    CID 1475820: Resource leak (RESOURCE_LEAK)
    Variable event going out of scope leaks the storage it points to.

Signed-off-by: Jonathan Rajotte <jonathan.rajotte-julien@efficios.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Change-Id: I705e3cc1a1894af52d6ddeee94798a887dc82bba