For HPDM 4.6, you cann't set specific privilege for just power management.
But with the new feature in HPDM 4.7 - Template privilege. You can specify different privilege for different template (include but not limited on Shutdown/reboot/WOL). Just simply create a group without the control of power management, then assign those user to the group.
Check the white paper - "WP_HPDM4.7_Privilege_Management_System.pdf"of new privilege system in HPDM 4.7: ftp://ftp.hp.com/pub/hpdm/Documentation/WhitePapers/4.7/