Set minimum protocol to SMB2

[ghost]

This sets the default configuration to use at least SMB2, instead of defaulting to SMB1. You may want to look into the sub versions of SMB2 to see if this default is correct.

[googlebot]

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[ttanxu]

Thanks for your effort to change it. Please sign Google CLA so that we can take your patch.

[ghost]

I signed it!

[googlebot]

CLAs look good, thanks!