test: add property index to support cloudant

[jannyHou]

Description

To unblock loopbackio/loopback-connector-cloudant#206.
We have the same fix in 3.x https://github.com/strongloop/loopback-datasource-juggler/blob/3.x/test/include.test.js#L1556

Related issues

• connect to <link_to_referenced_issue>

Checklist

• New tests added or existing tests modified to cover all changes
• Code conforms with the style
  guide

[jannyHou]

I believe the postgresql failure is not related:

13:45:16 sh: lerna: command not found
13:45:17 npm ERR! file sh
13:45:17 npm ERR! code ELIFECYCLE
13:45:17 npm ERR! errno ENOENT
13:45:17 npm ERR! syscall spawn
13:45:17 npm ERR! strong-globalize@4.0.8 postinstall: `lerna bootstrap`
13:45:17 npm ERR! spawn ENOENT
13:45:17 npm ERR! 
13:45:17 npm ERR! Failed at the strong-globalize@4.0.8 postinstall script.
13:45:17 npm ERR! This is probably not a problem with npm. There is likely additional logging output above.
13:45:17 
13:45:17 npm ERR! A complete log of this run can be found in:
13:45:17 npm ERR!     /home/jenkins/.npm/_logs/2019-06-19T17_45_17_702Z-debug.log
13:45:17 Build step 'Execute shell' marked build as failure
13:45:18 Archiving artifacts
13:45:18 [Cobertura] Publishing Cobertura coverage report...
13:45:18 
13:45:20 [BFA] Scanning build for known causes...
13:45:20 [BFA] No failure causes found
13:45:20 [BFA] Done. 0s
13:45:20 Triggering a new build of update-commit-status
13:45:20 Finished: FAILURE

But looking into the fix.

[dhmlau]

LGTM. Could you please see whether the postgresql failure is related to the changes? Thanks.

[jannyHou]

@dhmlau I believe the postgresql failure is not related, see my comment in #1750 (comment)