AndroidTarget: prevent concurrent invocations of 'logcat -c'

'adb logcat -c' has been observed to fail when called twice concurrently. Rather
than requiring all devlib users to fix their usage patterns, let's just delay
whenever clear_logcat is called twice.
1 file changed
tree: 3fd3e0b54b93f786363840d15c3815eb8ff09377
  1. devlib/
  2. doc/
  3. src/
  4. .gitignore
  5. README.rst
  6. setup.py