Port Minijail unit tests to Google Test.

Remove the duplicate unit test files.

Google Test is designed to be included directly with the project using
it, so add a simple shell script to get the sources.

Bug: 34520446
Test: Builds on Android, desktop Linux.
Change-Id: Iabc63fa1cb847b668645dbf5468454f025c93721

get_googletest.sh

diff --git a/get_googletest.sh b/get_googletest.sh
new file mode 100755
index 0000000..1708dcb
--- /dev/null
+++ b/get_googletest.sh
@@ -0,0 +1,6 @@
+#/bin/bash
+
+PV="1.8.0"
+
+wget -q -nc --secure-protocol=TLSv1 "https://github.com/google/googletest/archive/release-${PV}.tar.gz" -O "googletest-release-${PV}.tar.gz"
+tar zxvf "googletest-release-${PV}.tar.gz"