oo-admin-ctl-iptables-port-proxy: SELinux fix

Give input to iptables-restore on standard input instead of using command substitution.

Bash was expanding the <(...) command-substitution to a fifo, which oo-admin-ctl-iptables-port-proxy was then passing to the iptables-restore command as a command-line argument.  If oo-admin-ctl-iptables-port-proxy was being run from the /etc/init.d/openshift-iptables-port-proxy initscript, then Bash would have an SELinux context with type initrc_t, and it thus would create the fifo also with type initrc_t.  However, iptables-restore transitions SELinux contexts so that it is running with the iptables_t type.  The iptables-restore command would thus fail when it tried to open the fifo because SELinux policy blocks processes with type iptables_t from reading fifos with type initrc_t.

(Interestingly, the manpage for iptables-restore does not indicate that iptables-restore is even supposed to take a filename as an argument.)

This commit fixes bug 1020391.