envsetup: Wait for device in installboot/installrecovery

 * Useful when you're racing against a bug that causes a kernel panic
   shortly after USB turns on :(

Change-Id: I2a503e4b195e632ed5b67a77b942e80c47d0ff45
Merge branch 'cm-10.2' of https://github.com/CyanogenMod/android_build into cm-10.2