Rename "container" to "image"

- Updated `wwctl upgrade` to handle updates
- Maintained `.Container` and `.ContainerName` in tstruct
- Added `ContainerName()` methods to node and profile objects
- Added `--container`, `-C` aliases to wwctl commands (`<node|profile> <add|set>`)
- Added `wwctl container` alias
- Added support for `container_exit.sh` if `image_exit.sh` is not found

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

dracut/modules.d/90wwinit/parse-wwinit.sh

@@ -9,7 +9,7 @@ then
     uuid=$(dmidecode -s system-uuid)
     assetkey=$(dmidecode -s chassis-asset-tag | sed -E -e 's/(^ +| +$)//g' -e 's/^(Unknown|Not Specified)$//g' -e 's/ /_/g')
     wwinit_uri="$(getarg wwinit.uri)?assetkey=${assetkey}&uuid=${uuid}"
-    export wwinit_container="${wwinit_uri}&stage=container&compress=gz"; info "wwinit_container=${wwinit_container}"
+    export wwinit_image="${wwinit_uri}&stage=image&compress=gz"; info "wwinit_image=${wwinit_image}"
     export wwinit_system="${wwinit_uri}&stage=system&compress=gz"; info "wwinit_system=${wwinit_system}"
     export wwinit_runtime="${wwinit_uri}&stage=runtime&compress=gz"; info "wwinit_runtime=${wwinit_runtime}"
 
@@ -20,11 +20,11 @@ then
         export wwinit_tmpfs_size_option="-o size=${wwinit_tmpfs_size}"
     fi
 
-    if [ -n "${wwinit_container}" ]
+    if [ -n "${wwinit_image}" ]
     then
-        info "Found root=${root} and a Warewulf container image. Will boot from Warewulf."
+        info "Found root=${root} and a Warewulf image. Will boot from Warewulf."
         rootok=1
     else
-        die "Found root=${root} but no container image. Cannot boot from Warewulf."
+        die "Found root=${root} but no image. Cannot boot from Warewulf."
     fi
 fi