prefixArgs uses os.Setenv in e2e tests instead envMap.
This creates overwrites in some test cases and have an impact
on test quality and isolation between tests.
This PR uses ctlcontext envMap in each tests with high priority
and merges os environment variables with low priority.
The commit ensures that spawned etcdctl processes are "closed",
so they perform proper os wait processing.
This might have contributed to file-descriptor/open-files limit being
exceeded.
This change makes the etcd package compatible with the existing Go
ecosystem for module versioning.
Used this tool to update package imports:
https://github.com/KSubedi/gomove
