Automatic merge from submit-queue (batch tested with PRs 47626, 47674, 47683, 47290, 47688)

Use echoserver:1.6 for better debugging and XSS prevention.

**What this PR does / why we need it**: This updates our test code to use a newer echoserver with XSS preventions.

**Which issue this PR fixes**: fixes #47682

**Special notes for your reviewer**: Marking as 1.7 since it's a fix to test code.

**Release note**:
```release-note
NONE
```