scylla_util.py: Fix Azure support for machine-image
scylla_util.py: Fix Azure support for machine-image

In https://github.com/scylladb/scylla/pull/7807 we added support for
Azure instance in Scylla.

The following changes are required in order machine-image to work:
1) fix wrong metadata URL and updating metadata path values (was
   intreduce in
https://github.com/scylladb/scylla/commit/f627fcbb0c49618dc45b61d77b7b4a86682f18a2)
2) fix function naming which been used my machine image
3) add missing function which are reuqired by mahcine-image
4) cleanup unused functions

Closes #8596

scylladb/scylla,scylladb/scylla,scylladb/scylla,scylladb/scylla