Option Emulator executable is set to emulator64-x86. It is used correctly for starting avd but is ignored for snapshot listing as shown in log:
$ /opt/android-sdk-update-manager/tools/emulator -snapshot-list -no-window -avd hudson_en-US_480_WVGA_android-23_x86_64
sh: glxinfo: command not found
/opt/android-sdk-update-manager/tools/qemu/linux-x86_64/qemu-system-x86_64: error while loading shared libraries: libpulse.so.0: cannot open shared object file: No such file or directory
[android] Starting Android emulator and creating initial snapshot
[android] Erasing existing emulator data...
$ /opt/android-sdk-update-manager/tools/emulator64-x86 -engine classic -ports 5774,5775 -report-console tcp:5823,max=60 -avd hudson_en-US_480_WVGA_android-23_x86_64 -no-snapshot-load -no-snapshot-save -wipe-data -no-window -no-audio -gpu off
PS emulator64-x86 does not try to load libpulse.so.0, that's why this option is used.
PPS maybe it is worth adding log message that snapshot listing has failed