KeyScan.md sample code and server.FlushDatabase

[qcz]

Do you think it's wise to put server.FlushDatabase(); to the sample code in KeyScan.md without any comments? For a beginner user not aware of all Redis commands, and who searches for a sample code to get the list of the keys, it can be very deceiving (as it is not available anywhere else in the documentation).

[mgravell]

Fair comment, thanks; added comments here a816651