Fix negtive repeat command value issue.
Fix negtive repeat command value issue.

If command like "-1 set a b" is sent with redis-cli, it will cause a deadless loop. So some repeat value checking logic is added to avoid this.

oranagra/redis,pmem/redis,yossigo/redis,PKRoma/redis,antirez/redis,GitHubMota/redis,pmem/redis,oranagra/redis,neomantra/redis,spinlock/redis,PKRoma/redis,soveran/redis,charsyam/redis,ofirluzon/redis,ctripcorp/redis,PKRoma/redis,ctripcorp/redis,ctripcorp/redis,GitHubMota/redis,antirez/redis,neomantra/redis,ofirluzon/redis,ofirluzon/redis,nnog/redis,charsyam/redis,spinlock/redis,soloestoy/redis,soveran/redis,charsyam/redis,pmem/redis,charsyam/redis,soloestoy/redis,soveran/redis,yossigo/redis,spinlock/redis,soveran/redis,nnog/redis,oranagra/redis,spinlock/redis,GitHubMota/redis,GitHubMota/redis,oranagra/redis,nnog/redis,soloestoy/redis,oranagra/redis,soloestoy/redis,neomantra/redis,antirez/redis,pmem/redis,nnog/redis,antirez/redis,yossigo/redis,soloestoy/redis,yossigo/redis,neomantra/redis,neomantra/redis,PKRoma/redis,charsyam/redis,PKRoma/redis,ofirluzon/redis,yossigo/redis,ofirluzon/redis,ctripcorp/redis