- Move normalizeVersion to utils.NormalizeVersion for single source of truth
- Update agentupdate and dockeragent packages to use shared function
- Add 14 test cases for version normalization
This prevents bugs like issue #773 where a fix applied to one copy
but not the other caused an update loop.
When the agent binary is symlinked (e.g., from /opt/pulse/bin to
/usr/local/bin), the self-update would fail with "invalid cross-device
link" because os.Rename() doesn't work across filesystems.
Now resolves symlinks before update and creates the temp file in the
same directory as the real binary.
Related to #737
