To change the ospadmin UI password in OSPrey you must edit the xitami.aut file and then kill the xitami pid.
$ vi $OSPrey_HOME/xitami/xitami.aut
ospadmin="current-OSP-password"
The nexus_watchdog will automatically restart xitami after you kill the process ID.
[ospadmin@server ~]$ ps -ef|grep xitami
ospadmin 17124 17122 1 12:45 pts/7 00:02:13 xitami -w xitami -S -q
[ospadmin@server ~]$ kill -9 17124
[ospadmin@server ~]$
[ospadmin@server ~]$ ps -ef|grep xitami
ospadmin 10191 17122 0 15:54 pts/7 00:00:00 xitami -w xitami -S -q
ospadmin 10289 8971 0 15:54 pts/8 00:00:00 grep xitami