Remove extra test flags from all commands

Currently all commands are being build with extra flags. The extra
flags appear because of a direct import of the testing package from
the fake_etcd_client.go source file.

Remove the direct import of the testing package. Add a tools.T
interface to support existing behavior. Also clean up two TODO items
by remove using of the expectError and expectNoError functions.

Fixes #579
Merge pull request #647 from kelseyhightower/fix_extra_test_flags

Remove extra test flags from all commands