Add space

Add space between two online user:
From:
# Server: version=0.4.10, uptime=190.5, max_lag=0.001, clients={user1,user2,user3,user4,user5,foobar,userplayedminetestthismorning}
To be:
# Server: version=0.4.10, uptime=190.5, max_lag=0.001, clients={user1, user2, user3, user4, user5, foobar, userplayedminetestthismorning}