Change hard-coded temporary directory.

The properties tests creates a temporary directory in /data/nativetest,
but this directory might not exist in all circumstances.
Change this to create the temporary directory in /data/local/tmp.

Change-Id: I812d3e24fcd084c5d74055c9faa95b1656f255bc

Conflicts:
	tests/property_benchmark.cpp
	tests/system_properties_test.cpp