Fix unstable test cases

[supercaracal]

The following test case have been becoming unstable since I added several replica and Sentinel nodes for test. (ref: #816 #895)

redis-rb/test/distributed_remote_server_control_commands_test.rb

Lines 29 to 38 in 7127f3b

	def test_info_commandstats
	target_version "2.5.7" do
	r.nodes.each { |n| n.config(:resetstat) }
	r.ping # Executed on every node
	r.info(:commandstats).each do |info|
	assert_equal "1", info["ping"]["calls"]
	end
	end
	end

Sentinels keep pinging to the node for monitoring. So the stats was unintentionally incremented. I modified as not using PING stats.

irb(main):032:0> r.info(:commandstats).keys
=> ["publish", "ping", "info", "replconf", "config"]

irb(main):033:0> r.info(:commandstats)['ping']
=> {"calls"=>"51", "usec"=>"109", "usec_per_call"=>"2.14"}

irb(main):034:0> r.info(:commandstats)['ping']
=> {"calls"=>"56", "usec"=>"116", "usec_per_call"=>"2.07"}

irb(main):035:0> r.info(:commandstats)['ping']
=> {"calls"=>"63", "usec"=>"127", "usec_per_call"=>"2.02"}

irb(main):057:0> r.config :resetstat
=> "OK"

irb(main):058:0> r.info(:commandstats)['config']
=> {"calls"=>"1", "usec"=>"18", "usec_per_call"=>"18.00"}

irb(main):059:0> r.info(:commandstats)['config']
=> {"calls"=>"1", "usec"=>"18", "usec_per_call"=>"18.00"}

irb(main):060:0> r.config :get, 'port'
=> {"port"=>"6381"}

irb(main):061:0> r.info(:commandstats)['config']
=> {"calls"=>"2", "usec"=>"46", "usec_per_call"=>"23.00"}

[byroot]

Thanks a lot!