Cluster: Fix trib create when masters==replicas
Cluster: Fix trib create when masters==replicas

This bug was introduced in 2e5c394f during a refactor.

It took me a while to understand what was going on with
the code, so I've refactored it further by:
  - Replacing boolean values with meaningful symbols
  - Replacing 'i' with a meaningful variable name
  - Adding the proper abort check
  - Factoring out now duplicated conditionals
  - Adding optional verbose logging (we're inside *four*
    different looping constructs, so it takes a while to
    figure out where all the moving parts are)
  - Updating comment for the section

This fixes a problem when the number of master instances
equaled the number of replica instances.  Before, when
there were equal numbers of both, nodes_count would go to
zero, but the while loop would spin in i < @replicas because
i would never be updated (because the nodes_list of each ip
was length == 0, which triggered an endless loop of
next -> i = 0 -> 0 < 1? -> true -> next -> i = 0 ...)

Thanks to carlo who found this problem at:
https://groups.google.com/forum/#!topic/redis-db/_WVVqDw5B7c

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