Update rails cookbook bundler command to simulate a full login for the deploy user

I'm trying to utilize the Ruby Java Bridge (rjb) gem which has a compile dependency on the JAVA_HOME environment variable.  I've been able to get the setting included in the 'deploy' user's shell environment using the java::set_java_home recipe but it's not sticking due to the way we call the bundler.  The change I'm asking for solves the problem for me.