[server][hap] Fix misleading function & struct names concerned with self monitoring triggers

The name "AvailableTrigger" can't be ditinguished from normal
triggers, and it's not matched with the command name
"HAPI_CMD_SEND_HAP_SELF_TRIGGERS".
Merge pull request #724 from project-hatohol/fix-misleading-self-triggers

[server][hap] Fix misleading function & struct names concerned with self...