Implement BRUTEFORCE_SPEED respect (telnet)

This implements just for telnet, but assuming this strategy is kosher,
it's not too painful to add for the rest of the LoginScanner using the
old defaults used by `AuthBrute`.

See #3904, @dmaloney-r7 or @jlee-r7
Fix some double spacing
Add a spec for the Base LoginScanner

Turns out, there wasn't one.

This tests what I've changed, at least.
Add a bruteforce_speed option to all LoginScanners
Explicitly include the HTTP Login scanner

This should be the last commit that fixes #3904.
Don't lie about stop_on_success

This absolutely needs to be honored too, though.

See #4365.
Merge pull request #4364 from todb-r7/bug/bruteforce-speed-3904

Modules should respect bruteforce_speed again