A round of _reactors_scheduler_gather_metrics should be stopped when there is calloc failure. Change-Id: Ic2220c561abb07a849ea37d3c88af3f6d5d1ffa1 Signed-off-by: Liu Xiaodong <xiaodong.liu@intel.com> Reviewed-on: https://review.spdk.io/gerrit/c/spdk/spdk/+/4882 Reviewed-by: Tomasz Zawadzki <tomasz.zawadzki@intel.com> Reviewed-by: Jim Harris <james.r.harris@intel.com> Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>