Revision 1909351

Revert r1845377 as it has caused a lot of trouble for end users.

Plaintext password storage will again be enabled by default. It can still be 
disabled at configure time.

* configure.ac: Invert the default of the plaintext-password-storage
   option and update its help text.

Discussed on dev@:
https://lists.apache.org/thread/9cswoh8wdnvdd81wp0sr7dtw2fnrwox0