Fix: sessiond: assertion on inconsistent filter bytecode and expression

Fix: sessiond: assertion on inconsistent filter bytecode and expression

The session daemon correctly expects that a recording event-rule that
specifies a filter must have both a bytecode and an expression (or
neither of them).

However, it shouldn't assert as those elements are user-specified. The
handling is changed to return an "invalid parameter" error to the
client.

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Change-Id: I3df6ce79bc6ce1fa9dadb184a7fd2b528dc2a597