GoogleServicesPlugin::getJsonLocations not returning all expected paths

**Describe the bug**
The current implementation of the `GoogleServicesPlugin::getJsonLocations` concatenates `fileLocation` variable with new flavor values without ever reseting it to the `src` value. So the function with input paramters `('buildType', ['first', 'second'])` only returns `src/first/google-services.json` and not the `src/second/google-services.json` as the location to look for (it'll return `src/first/second/google-services.json` path instead).

**To Reproduce**
Steps to reproduce the behavior:
1. Call `GoogleServicesPlugin::getJsonLocations` with input parameters where flavor list is longer than one
2. Check the contents of the list that's returned from `GoogleServicesPlugin::getJsonLocations`

**Expected behavior**
`GoogleServicesPlugin::getJsonLocations` returns `src/flavorName/google-services.json` for every `flavorName` in the input parameter list.

**Desktop (please complete the following information):**
- Plugin name and version: current HEAD @ `master`

**Additional context**
Here's a small kotlin snippet that tests the returned values for multi flavor input [https://pl.kotl.in/NE02tm42_](https://pl.kotl.in/NE02tm42_)