limit webtest getObjects() to 10 (rebased onto dev_5_0)



This is the same as gh-2253 but rebased onto dev_5_0.

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This fixes getObjects("Image") and getObjects("Dataset") on the webtest homepage, which were attempting to get ALL objects available to that user. Now this is limited to 10 each.

This has no effect on functionality, but should mean that running this on a server with a large number of available images causes no performance problems or server crash.