iptables: GetProxyPort(): run iptables quietly
iptables: GetProxyPort(): run iptables quietly

GetProxyPort() runs an iptable command to determine a previously
installed port. The command will fail if the CILIUM_PRE_mangle chain
does not exist. This is fine: GetProxyPort() will return 0 which
results in the selecting a new available port.

A failed command, however, will result in spurious error messages:

level=error msg="Command execution failed" cmd="[iptables -t mangle -n -L CILIUM_PRE_mangle]" error="exit status 1" subsys=iptables
level=warning msg="iptables: No chain/target/match by that name." subsys=iptables
levelevel=debug msg="DNS Proxy port is configured to 0. A random port will be assigned by the OS."

Pass the quiet flag when executing the command to avoid this.

Fixes: https://github.com/cilium/cilium/issues/15002

Signed-off-by: Kornilios Kourtis <fbd1fdd48e316a736711a3b30106195507321a09@isovalent.com>

tklauser/cilium,michi-covalent/cilium,michi-covalent/cilium,cilium/cilium,michi-covalent/cilium,tgraf/cilium,tklauser/cilium,michi-covalent/cilium,tgraf/cilium,cilium/cilium,tklauser/cilium,tgraf/cilium,cilium/cilium,michi-covalent/cilium,tgraf/cilium,tgraf/cilium,cilium/cilium,cilium/cilium,tklauser/cilium,tgraf/cilium,tklauser/cilium