AdbdCommunicationMode: choose default from API level

propertyFile_getAdbdCommunicationMode:  If API level <16, force
"ro.adb.qemud" to 0.  If API level >= 16, use value from
"ro.adb.qemud" or default to 1

(commit c13daef7bdc0982084 "Use QEMU pipe for ADB communication"
was first released in API 16 system images)

Refactored integer parsing, memory management and validation code into
propertyFile_getInt

Added unit tests for propertyFile_getInt/ApiLevel/AdbdCommunication

Change-Id: I32e3e16aa4e183546936c4841d071bd709c0780e
3 files changed