Incompatibilty of citus with Scientific Linux

Scientific Linux is a distro out of FermiLab that is used in several national labs. It is based on RHEL.
I have been unsuccessful in running citus: the installation script was successful but executing SQL commands that communicate between the coordinator and workers results in messages:
```
# select run_command_on_workers($$select 1$$);
ERROR: epoll_ctl() failed: No such file or directory
CONTEXT: PL/pgSQL function run_command_on_workers(text,boolean) line 13 at RETURN QUERY
```
Looking at the output of strace confirms there is an error in a call to epoll_ctl. It certainly looks like a networking issue but it's not a port blockage in our network and sestatus tells me SELinux is disabled.

Start by reproducing the failure on Scientific Linux using run_command_on_workers($$select 1$$), then compare the behavior with the reported strace output and epoll_ctl error. Determine whether the failure is in Citus, PostgreSQL interaction, or the operating-system environment; done means worker communication succeeds without the error.

Written by the indexing model from the issue text.