I found the problem! SLES 12 is now enforcing a range limit on the pri= value specified in /etc/fstab.

From /var/log/messages:
Code:
2017-09-05T18:36:33.401209-05:00 wcs-mf-winxs-db2t systemd[1]: Failed to parse swap priority "pri=-2", ignoring: Numerical result out of range
2017-09-05T18:36:33.401211-05:00 wcs-mf-winxs-db2t systemd[1]: Activating swap /dev/disk/by-path/ccw-0.0.0202-part1...
2017-09-05T18:36:33.401214-05:00 wcs-mf-winxs-db2t systemd[1]: Failed to parse swap priority "pri=-1", ignoring: Numerical result out of range
2017-09-05T18:36:33.401217-05:00 wcs-mf-winxs-db2t systemd[1]: Activating swap /dev/disk/by-path/ccw-0.0.0201-part1...
Unfortunately, it is enforcing the wrong range. Here is the 'pri=' sections from the man page for swapon(8), on SLES 12 SP2:
Code:
       -p, --priority priority
              Specify the priority of the swap device.  priority is a value between -1 and 32767.  Higher numbers indicate higher priority.  See swapon(2) for  a  full  description  of
              swap priorities.  Add pri=value to the option field of /etc/fstab for use with swapon -a.  When no priority is defined, it defaults to -1.

Harley