*: replace path.Join on files with filepath.Join

[heyitsanthony]

Full audit of codebase. Continuation of #7515

[heyitsanthony]

can squash into single commit if it makes sense; a lot of commits in this one...

[codecov-io]

Codecov Report

❗ No coverage uploaded for pull request base (master@d78b03f). Click here to learn what that means.
The diff coverage is 93.54%.

@@           Coverage Diff            @@
##             master   #7518   +/-   ##
========================================
  Coverage          ?   70.2%           
========================================
  Files             ?     320           
  Lines             ?   26203           
  Branches          ?       0           
========================================
  Hits              ?   18397           
  Misses            ?    6347           
  Partials          ?    1459

Impacted Files	Coverage Δ
etcdctl/ctlv3/command/snapshot_command.go	64.77% <100%> (ø)
etcdctl/ctlv3/command/migrate_command.go	63.78% <100%> (ø)
embed/etcd.go	67.22% <100%> (ø)
etcdserver/config.go	77.21% <100%> (ø)
etcdserver/server.go	79.37% <100%> (ø)
pkg/transport/listener.go	85.5% <100%> (ø)
etcdctl/ctlv2/command/backup_command.go	55.55% <100%> (ø)
etcdmain/etcd.go	45.33% <100%> (ø)
snap/db.go	64.51% <100%> (ø)
mvcc/backend/backend.go	73.75% <100%> (ø)
... and 4 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update d78b03f...2f1542c. Read the comment docs.

[xiang90]

LGTM. I am wondering how etcd managed to work on windows before...

[gyuho]

don't think we would backport these. we can just merge them?