I have two set of nearly identical jobs. One of them runs 4.1.2 emulators and the other one runs 4.4 emulators. I found that the jobs run 4.4 emulators has significantly higher chance of timeout during emulator launch. In fact, the 4.1.2 emulators almost never fail to launch.
I've also upgraded to 2.11.1 and things got significantly worse. The launch time was a lot longer, and launch timeout happened a lot more frequently. There is a similar thread in StackOverFlow: http://stackoverflow.com/questions/23699433/android-emulator-jenkins-plugin-not-working