COMMAND: fix argument parsing.
COMMAND: fix argument parsing.

This fixes detection of wrong subcommand (that resulted in the default
all-commands output instead) and allows COMMAND INFO to be called
without arguments (resulting into an empty array) which is useful in
programmtically generated calls like the following (in Ruby):

    redis.commands("command","info",*mycommands)

Note: mycommands may be empty.

JackieXie168/redis,JackieXie168/redis,JackieXie168/redis,JackieXie168/redis