Use prefix status codes for older FTP implementations

Some older FTP implementations send 125 status codes instead of 150. Under the spec, both are valid, as should all 1xx status codes. (thought they could possible indicate additional work?)

This changes the resulting expectations.

This means that in addition to a 125, the following are also valid:

110 - Restart marker replay . In this case, the text is exact and not left to the particular implementation; it must read: MARK yyyy = mmmm where yyyy is User-process data stream marker, and mmmm server's equivalent marker (note the spaces between markers and "=").
120	- Service ready in nnn minutes.

I am not familiar enough with FTP to know what the implication of expecting these codes are, but this solution is good enough for us...

If you have any feedback on how to make it more reliable, let me know!