Fix netcat option in udp_check.sh for CentOS/RHEL
Fix netcat option in udp_check.sh for CentOS/RHEL

-w (timeout) option doesn't do anything in nmap-ncat (default netcat in
CentOS/RHEL) for UDP datagrams, and nmap-ncat has a default idle timeout
set to 2 seconds.
We can get the same behavior as netcap-openbsd (Debian/Ubuntu) by
setting that idle timeout (-i) option to 1 second.

This commit detects the flavor of the netcat binary (nmap vs other) and
uses it to adapt the parameters.

Story: 2007688
Task: 39800

Change-Id: I0100aaa428477f011bd39a90dd4ec98199b4bebc

openstack/octavia,openstack/octavia,openstack/octavia