Use the locate service to retrieve a server

[bassosimone]

As specified in the spec of ndt7, we should use the locate service to find out the closest server and then run the test with such server. As pointed out by many this repository is still using an hardcoded server name, which is the IP address of a GCE instance I used for testing.

[stevepopovich]

Is this still the case? New to this source code, but it looks like the library does this:

ndt7-client-android/libndt7/src/main/java/net/measurementlab/ndt7/android/NDTTest.kt

Line 113 in 3e831b7

private fun getHostname(): Call? {

ndt7-client-android/libndt7/src/main/java/net/measurementlab/ndt7/android/NDTTest.kt

Line 42 in 3e831b7

getHostname()?.enqueue(