Update network interface bonding configuration and documentation

- Closes: #1482
- Closes: #1280

This also corrects poor handling of whitespace around the "file" function
throughout the templates, given experiences with the network templates while
implementing the bond behavior. Since the file function actually does produce
output (that is parsed by Warewulf itself) it should not collaps prefix
whitespace.

Signed-off-by: Jonathon Anderson <janderson@ciq.com>

overlays/ifcfg/internal/ifcfg_test.go

@@ -72,9 +72,9 @@ func Test_ifcfgOverlay(t *testing.T) {
 const ifcfg string = `backupFile: true
 writeFile: true
 Filename: ifcfg-default.conf
-# This file is autogenerated by warewulf
 
-TYPE=ethernet
+# This file is autogenerated by warewulf
+TYPE=Ethernet
 DEVICE=wwnet0
 NAME=default
 BOOTPROTO=static
@@ -87,12 +87,13 @@ IPV6INIT=yes
 IPV6_AUTOCONF=yes
 IPV6_DEFROUTE=yes
 IPV6_FAILURE_FATAL=no
+DNS1=1.1.1.1
+DNS2=1.0.0.1
 backupFile: true
 writeFile: true
 Filename: ifcfg-secondary.conf
 # This file is autogenerated by warewulf
-
-TYPE=ethernet
+TYPE=Ethernet
 DEVICE=wwnet1
 NAME=secondary
 BOOTPROTO=static
@@ -119,8 +120,8 @@ HOSTNAME=node1
 const ifcfg_vlan string = `backupFile: true
 writeFile: true
 Filename: ifcfg-tagged.conf
-# This file is autogenerated by warewulf
 
+# This file is autogenerated by warewulf
 VLAN=yes
 DEVICE=eth0.902
 NAME=tagged
@@ -135,8 +136,7 @@ backupFile: true
 writeFile: true
 Filename: ifcfg-untagged.conf
 # This file is autogenerated by warewulf
-
-TYPE=ethernet
+TYPE=Ethernet
 DEVICE=eth0
 NAME=untagged
 BOOTPROTO=static
@@ -151,8 +151,10 @@ IPV6_FAILURE_FATAL=no
 const ifcfg_routes string = `backupFile: true
 writeFile: true
 Filename: route-tagged.conf
+
 # This file is autogenerated by warewulf
 192.168.1.0/24 via 192.168.2.254
+
 backupFile: true
 writeFile: true
 Filename: route-untagged.conf