increase-emulator-start-time-limit: Increase limit from 180s to 360s

I'm submitting this for feedback, but not necessarily for merging as is.

The emulator sometimes takes more than 180 seconds, the hard coded time
limit([1])([2]), to be ready, when starting from a snapshot.

[1]: https://github.com/jenkinsci/android-emulator-plugin/blob/9b91a1bb1c99be0b5371f0ada2992bd6ed51d503/src/main/java/hudson/plugins/android_emulator/AndroidEmulator.java#L63
[2]: https://github.com/jenkinsci/android-emulator-plugin/blob/9b91a1bb1c99be0b5371f0ada2992bd6ed51d503/src/main/java/hudson/plugins/android_emulator/AndroidEmulator.java#L381

The plugin increases the time limit by a factor of 4 when it's not using
a snapshot.

I saw the non-snapshot scenario take between 400 and 500 seconds to get
the emulator ready.

I increased the time limit to 360 s, and reduced the factor from 4 to 2.