This addresses three issues:
[1] Adding/removing an allowed sasl mechanism from a preexisting list
requires a restart to take effect
[2] Restarting the server twice causes the allowed sasl mech list to
get truncated
[3] Crash when using sasl PLAIN mechanism
https://pagure.io/389-ds-base/issue/49379
https://pagure.io/389-ds-base/issue/raw/files/888f686d3c35ab4c7e960e45b2f...