Addresses O'Reilly copyedits for Network Troubleshooting

Change-Id: I0fecfa63be466f9ead3fa9f5a31280485af274e9
Copy edits from O'Reilly for Maintenance, Failures, and Debugging

Change-Id: I81944761305d490efaca338f96b6494057f133d3
Merge "Addresses O'Reilly copyedits for Network Troubleshooting"
Merge "Copy edits from O'Reilly for Maintenance, Failures, and Debugging"