"--opbeans-node-agent-local-repo=/some/local/dir" doesn't work

[trentm]

The compose.py script supports some --opbeans-$lang-agent-local-repo=$localDir options to have the opbeans-$lang container use an APM agent from the given $localDir (a working copy of the APM agent repo). For example:

% ./scripts/compose.py start master --with-opbeans-node \
    --opbeans-node-agent-local-repo=~/el/apm-agent-nodejs5

Two issues using the node.js version of this option:

1. It doesn't actually install the Node.js APM agent from the local repo in a way that the opbeans-node installed at "/app" uses it.
2. Part of the handling for this involves making a copy of the local repo dir (to not pollute it). Unfortunately the local repo dir can have a somewhat weighty node_modules dir, which can take a long time (sometimes too long, resulting in the container being marked as unhealthy).

In my case:

% docker exec -ti 699d48159443 /bin/sh
/app # cd ~/local-install/
~/local-install # du -sh .
484.3M	.
~/local-install # du -sh node_modules
370.9M	node_modules
~/local-install # du -sk * | sort -n | tail -3
1516	test
101288	build
379756	node_modules

That's copying almost half a GiB for every ./scripts/compose.py start ....

PR coming to attempt to fix these.