Setting current working directory for dev server.

Summary:
* This allows `react-native` to work for users on fedora.
* `react-native run-android` was failing because the launch packager script was unable to find packager.sh (see `source` in `man bash`).
* This change sets cwd for the dev server when run with `run-android`.
Closes facebook/react-native#7316

Differential Revision: D3255866

fb-gh-sync-id: 88f6b18f7c61636ce8fecef77f7f4e60b1d9a637
fbshipit-source-id: 88f6b18f7c61636ce8fecef77f7f4e60b1d9a637

launchPackager.command

@@ -13,7 +13,7 @@ clear
 
 THIS_DIR=$(dirname "$0")
 pushd "$THIS_DIR"
-source packager.sh
+source ./packager.sh
 popd
 
 echo "Process terminated. Press <enter> to close the window"