Fix: syscall event rule: emission sites not compared in is_equal

Fix: syscall event rule: emission sites not compared in is_equal

The emission sites are not compared when comparing two kernel-syscall
event rules. This prevents users from subscribing to notifications of
triggers that use event-rule-matches syscall conditions which differ
only by their emission site (entry, exit, entry+exit).

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Change-Id: Id15eb682cd40f4966ca10911314ae7e8839712da