Bug fix: Remove signal blocking when disabling a perf event
Bug fix: Remove signal blocking when disabling a perf event

When sample-sources calls stop, it means to disable temporarily, and it
doesn't mean to stop definitely.
In this case, PERF_EVENT_IOC_DISABLE is sufficient.

HPCToolkit/hpctoolkit,HPCToolkit/hpctoolkit,HPCToolkit/hpctoolkit,HPCToolkit/hpctoolkit,HPCToolkit/hpctoolkit,HPCToolkit/hpctoolkit