lttng: Fix Resource View for traces without sched_switch events

lttng: Fix Resource View for traces without sched_switch events

The Resource View assumes that if the base quark of a resource is
present, the "Status" sub-attribute will always be there. This may
not be the case, for example if the trace does not have sched_switch
events enabled, but has shed_wakeup.

Change-Id: Iaf25cf3d8a5b8ee686281dc3064f241229c2c245
Signed-off-by: Alexandre Montplaisir <alexmonthy@voxpopuli.im>
Reviewed-on: https://git.eclipse.org/r/36492
Tested-by: Hudson CI
Reviewed-by: Marc-Andre Laperle <marc-andre.laperle@ericsson.com>
Tested-by: Marc-Andre Laperle <marc-andre.laperle@ericsson.com>