Move python-adb to development/python-packages.

Nothing else was being imported from system/core yet, and a path under
development makes more sense for this.

Bug: http://b/22881740
Change-Id: Ib0beb02137805b3e382535514a2bc067b7fd1d33
diff --git a/envsetup.sh b/envsetup.sh
index fa4e2d6..fcf3b47 100644
--- a/envsetup.sh
+++ b/envsetup.sh
@@ -183,7 +183,7 @@
     fi
 
     export PATH=$ANDROID_BUILD_PATHS$PATH
-    export PYTHONPATH=$T/system/core:$PYTHONPATH
+    export PYTHONPATH=$T/development/python-packages:$PYTHONPATH
 
     unset ANDROID_JAVA_TOOLCHAIN
     unset ANDROID_PRE_BUILD_PATHS