Ouch... Looks like you have some hope of using a previous version for now (or longer?): [URL] os_dependent files for el7 are available for that version: [URL]
Just tried to install srvadmin-all from [URL] and its pointing to the empty repo [URL] I cant see it listed in here either [URL] CentOS 7 is still supported until 2024‑06‑30 and is the basis for xenserver and xcp-ng so has broken the abilty to install srvadmin-all on the latest version of these hypervisors. 
Has Centos7 support just been removed for DSU