Fix bug of Concepts downloaded during forms download replacing those available under 'Manage concepts' setting

As of mUzima app for health providers version 2.4.0, when new concepts are downloaded during additional form download, the new concept list replaces the concepts available under the Manage concepts setting.  However, when the app is relaunched afresh, the full concepts list comprising both the previously existing concepts as well as those newly downloaded becomes available under the setting.

Steps to reproduce:

• Do an initial setup with a setup config that has some concepts (e.g Lwala Setup)
• Check to see which concepts are available under the Manage concepts setting. (For Lwala Setup, you'll see Weight, Height, and HIV (POS)
• Go to forms tab and download an additional form. Ensure that additional concepts are downloaded alongside the form download. (E.g, download the CDM Screening Form. For this form, you may allow the following concepts that are automatically parsed from the form get downloaded: Return Visit Date, Serum Glucose, Systolic Blood Pressure, Diastolic Blood Pressure, Body Mass Index and Referrals Ordered.)
• Once the additional form is downloaded, check to see which concepts are available under the Manage concepts setting. You'll notice that the newly downloaded concepts replace the pre-existing list. (The expectation is that both the newly downloaded and the pre-existing concepts list should be available under the _Manage concepts setting)_
• Close the app completely, login afresh and then check to see which concepts are available under the Manage concepts setting. You'll notice that both the newly downloaded and the pre-existing concepts list is available.