Fix "Install from URL" and "Install from WEB" - be more flexible [#33316]

Currently the "Install from URL" and "Install from WEB" tasks fail in some special cases.

#### Test:
Try the "Install from URL" task with the following URL:
https://github.com/jtester/TestExtension/archive/1.0.zip

**Expected**: Installation successful
**Actual**: Unable to find install package

#### Test2:
Download the package first and install via "Upload"

**Expected**: Installation successful
**Actual**: Installation successful

Apply the patch

The "Install from URL" task should work now.

Ref: Old bug tracker: http://joomlacode.org/gf/project/joomla/tracker/?action=TrackerItemEdit&tracker_item_id=33316