scope: do not disable timer event source when state is SCOPE_RUNNING

scope: do not disable timer event source when state is SCOPE_RUNNING

In scope_set_state(), the timer event source may be disabled depending
on the state. Currently, it will be disabled when the state is
SCOPE_RUNNING. This has the effect of new RuntimeMaxSec values being
ignored on coldplug.

Note that this issue is not currently present when scopes are started
because when scope_start() is called, scope_arm_timer() is called after
scope_set_state().