*: fill out blank package godocs

Mostly one-liner short descriptions, but also includes some typo fixes
and some examples.

tools/functional-tester/etcd-runner/command/root.go

@@ -12,6 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+// Package command implements individual etcd-runner commands for the etcd-runner utility.
 package command
 
 import (