dcnm_inventory: Fix set_role issue

[mikewiebe]

Summary

• Resolves dcnm_inventory: Invalid JSON response: Cannot deserialize value of type #486
• And issue in nightly NaC run

TASK [cisco.nac_dc_vxlan.create : Manage Interface Trunk in Nexus Dashboard] **************************************************************************************************************************************
Tuesday 05 August 2025  17:24:32 -0400 (0:00:00.022)       0:11:29.062 ******** 
Tuesday 05 August 2025  17:24:32 -0400 (0:00:00.021)       0:11:29.061 ******** 
fatal: [nac-ibgp-fabric1]: FAILED! => {"changed": false, "module_stderr": "'CDP_ENABLE'", "module_stdout": "", "msg": "MODULE FAILURE: No start of json char found\nSee stdout/stderr for the exact error"}