Set cts-tradefed paths to absolute

Setting the CTS_ROOT path to absolute in cts-tradefed allows to run the script
from different location.

Test: run CTS manually

Change-Id: I311fe0b8286e7a40db34dd137f4af949e9936c65
Signed-off-by: Milosz Wasilewski <milosz.wasilewski@linaro.org>
diff --git a/tools/cts-tradefed/etc/cts-tradefed b/tools/cts-tradefed/etc/cts-tradefed
index 3e935ca..00f51af 100755
--- a/tools/cts-tradefed/etc/cts-tradefed
+++ b/tools/cts-tradefed/etc/cts-tradefed
@@ -76,7 +76,7 @@
 
 if [ -z ${CTS_ROOT} ]; then
     # assume we're in an extracted cts install
-    CTS_ROOT="$(dirname $0)/../.."
+    CTS_ROOT="$(dirname $(readlink -e $0))/../.."
 fi;
 
 JAR_DIR=${CTS_ROOT}/android-cts/tools