switch appium-discuss links from google-groups to discourse
Merge pull request #3525 from Jonahss/master

switch appium-discuss links from google-groups to discourse
add test to prove we can close and re-launch an app mid-session
fix async bug in ios crash waterfall
previously, we'd respond to the client's current callback and then start
the shutdown sequence. this opened up a situation where the client could
then call another command (say driver.quit) during shutdown, enabling
the possibility of two simultaneous shutdown flows causing undefined
behavior. this fix makes sure we don't respond to the client for a
command that caused a crash until we're done shutting down.