addjobCommand implementation improved for clarity and behavior
addjobCommand implementation improved for clarity and behavior

In 6c878c9 a serious bug in the job replication was fixed. This commit
attempts to improve the fix in the following ways:

* Use a new variable that just states if we are going to drop the job
  from memory before returning to the caller. This happnes only in one
  case actually: when the job is externally replicated because of memory
  warning level AND at the same time ASYNC replication is choosen by the
  user.

* Instead of putting the job into the scheduler skiplist, and later
  remove it, we directly avoiding putting the job into the scheduler if
  we are going to free it.

* The job is not put into AOF if we don't plain to retain a copy in the
  local node.

Related to Pull Request #83.

felixbuenemann/disque,lamby/disque,ErikDubbelboer/disque,jmptrader/disque,seppo0010/disque,gideonairex/disque,gideonairex/disque,c2j/disque,c2j/disque,themage/disque,chen-tian/disque,lamby/pkg-disque,themage/disque,GrimDerp/disque,tempbottle/disque,lamby/pkg-disque,antirez/disque,themage/disque,chen-tian/disque,ErikDubbelboer/disque,hanicker/disque,sunheehnus/disque,Koed00/disque,sunheehnus/disque,jmptrader/disque,felixbuenemann/disque,hanicker/disque,CodyReichert/disque,lamby/disque,mopuri-sandeep/disque,tempbottle/disque,CodyReichert/disque,mopuri-sandeep/disque,GrimDerp/disque,antirez/disque,seppo0010/disque,Koed00/disque,jmptrader/disque