Fix: uninitialized variable may be used in local rotation check

** CID 1395985:  Uninitialized variables  (UNINIT)

'ret' may be left uninitialized if no consumer daemons are
iterated-upon to perform a local rotation pending check.

In practice this wont' happen as that would mean that the
ltt_session has no user space nor kernel session action, thus
no rotation would be launched.

Reported-by: Coverity Scan
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>