Cluster: clear the FAIL status for masters without slots.
Cluster: clear the FAIL status for masters without slots.

Masters without slots don't participate to the cluster but just do
redirections, no need to take them in FAIL state if they are back
reachable.

spearhead-ea/redis,louisliangjun/redis,maodeyi/redis_lua,xuzhezhaozhao/redis_reading,slfs007/mk-redis,HunanTV/redis,ksarch-saas/redis,slfs007/mk-redis,Hailei/redis,ttuna/msot-redis,slfs007/mk-redis,MSOpenTech/redis,darksideofthemoo/redis-histogram,ttuna/msot-redis,louisliangjun/redis,xuzhezhaozhao/redis_reading,HunanTV/redis,xuzhezhaozhao/redis_reading,MSOpenTech/redis,maodeyi/redis_lua,splitice/redis,MSOpenTech/redis,MSOpenTech/redis,MSOpenTech/redis,himoca/redis,ramonsnir/redis,spearhead-ea/redis,maodeyi/redis_lua,spearhead-ea/redis,Hailei/redis,ramonsnir/redis,ksarch-saas/redis,himoca/redis,louisliangjun/redis,Hailei/redis,ksarch-saas/redis,splitice/redis,splitice/redis,jxwr/redis,ksarch-saas/redis,darksideofthemoo/redis-histogram,HunanTV/redis,ttuna/msot-redis,louisliangjun/redis,ttuna/msot-redis,ttuna/msot-redis,Hailei/redis,jxwr/redis,xuzhezhaozhao/redis_reading,ramonsnir/redis,himoca/redis,jxwr/redis,splitice/redis,darksideofthemoo/redis-histogram,darksideofthemoo/redis-histogram,HunanTV/redis