Wait for dev.bootcomplete property on emulator launch

[plastiv]

Pull dev.bootcomplete instead of init.svc.bootanim system property to allow -no-boot-anim emulator start option.

From documentation: https://developer.android.com/studio/run/emulator-commandline#startup-options

-no-boot-anim
Disable the boot animation during emulator startup for faster booting. On slower computers, this option can significantly speed up the boot sequence.

Who doesn't want faster booting? It also looks like AndroidStudio is using this property as well https://android.googlesource.com/platform/tools/adt/idea/+/studio-master-dev/android/src/com/android/tools/idea/avdmanager/EmulatorConnectionListener.java#142

I'm not too familiar with swarmer internals or RxJava. But at my sandbox repo dev.bootcomplete is available on all x86 emulators api15-28 https://travis-ci.org/plastiv/peta-androidsdk/builds/502602101

I can work on integrating CI for swarmer separately if you are interested.