RFR: 8255078: sun/net/ftp/imp/FtpClient$MLSxParser uses wrong datetime format

[Igor Ignatyev]

Hi all,

could you please review this small patch?

according to [RFC3659](https://tools.ietf.org/html/rfc3659), time values in MLSx response have the following format:
>    time-val = 14DIGIT [ "." 1*DIGIT ]
> 
>    The leading, mandatory, fourteen digits are to be interpreted as, in
>    order from the leftmost, four digits giving the year, with a range of
>    1000--9999, two digits giving the month of the year, with a range of
>    01--12, two digits giving the day of the month, with a range of
>    01--31, two digits giving the hour of the day, with a range of
>    00--23, two digits giving minutes past the hour, with a range of
>    00--59, and finally, two digits giving seconds past the minute, with
>    a range of 00--60 (with 60 being used only at a leap second). Years
>    in the tenth century, and earlier, cannot be expressed. This is not
>    considered a serious defect of the protocol.
> 
>    The optional digits, which are preceded by a period, give decimal
>    fractions of a second. These may be given to whatever precision is
>    appropriate to the circumstance, however implementations MUST NOT add
>    precision to time-vals where that precision does not exist in the
>    underlying value being transmitted.
> 
>    Symbolically, a time-val may be viewed as
> 
>   YYYYMMDDHHMMSS.sss
> 
>    The "." and subsequent digits ("sss") are optional. However the "."
>    MUST NOT appear unless at least one following digit also appears.
> 

`MLSxParser`, however, uses `SimpleDateFormat("yyyyMMddhhmmss")` (which is wrong b/c it uses `hh` instead of `HH` and
doesn't account for optional `.sss`) to parse modify/create facts and ignore any parse exceptions.

`FtpClient` actually already has and uses `SimpleDateFormat` w/ right formats in `getLastModified` where it parses MDTM
response, the patch refactors the code to reuse the same `SimpleDateFormat` in `MLSxParser`.

testing:
* [ ] tier1
* [ ] `test/jdk/sun/net` on `{linux,windows,macosx}-x64`

-------------

Commit messages:
 - 8255078: sun/net/ftp/imp/FtpClient$MLSxParser uses wrong datetime format

Changes: https://git.openjdk.java.net/jdk/pull/776/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=776&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8255078
  Stats: 50 lines in 1 file changed: 19 ins; 23 del; 8 mod
  Patch: https://git.openjdk.java.net/jdk/pull/776.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/776/head:pull/776

PR: https://git.openjdk.java.net/jdk/pull/776