Fix sockproc possibly inheriting nginx's sockets/file descriptors

[GUI]

When we launch the sockproc process from inside nginx, we explicitly try to clear all extra file descriptors, so nginx doesn't inherit the nginx processes sockets. If sockproc does inherit these sockets, then if nginx gets stopped or restarted, sockproc takes over listening on those sockets, which means nginx can't be started again.

However, the existing implementation of clearing these file descriptors could fail under certain circumstances, leading to nginx being unable to restart. It depends on how nginx is started, but this could reliably fail under this scenario:

• nginx was started under an init script.
• nginx had worker processes running as a less privileged user.
• The user that originally ran the init start command was "cd"ed into a directory that the less privileged nginx worker user didn't have permissions to be in.

This was failing due to the find command being combined with -exec basename to find the file descriptors to clear. basename would fail if the current user didn't have permissions to be in the current directory (even if it was only finding the basename of paths in /proc which it did have permissions to). This led to no file descriptors being cleared. The find command would also generate a warning message after finishing about not being able to restore the initial directory.

To fix this:

• Our script to start sockproc now explicitly sets the current directory to /, so any commands that require permissions to be in the current directory should work.
• Extract the basename of the /proc/ paths using bash, instead of shelling out to the basename command.
• If for any reason, clearing the file descriptors based on /proc/ paths fails, also fallback to the more naive OS x approach in Linux too.

A test has been added to the test suite to test this behavior. Since the Makefile was getting a little unwieldy (particularly with another test that needed all the "worker perms" environment variables), shift the commands used to run the tests into a wrapper shell script to make things a bit easier to manage.