Fix install_cni_chaining not creating CNI conf correctly in some cases

The chaining CNI conf was not created correctly under two conditions:

1. If there is non CNI conf file in the directory, like a kubeconfig
   required by the primary CNI.
2. If the CNI conf file is created but not completely written yet.

The patch ensures it only selects valid CNI conf and waits for it to be
written before using it to create the chaining CNI conf.

Signed-off-by: Quan Tian <quan.tian@broadcom.com>

build/images/scripts/install_cni_chaining

@@ -50,7 +50,8 @@ done
 
 # Find the cni conf file with lowest name, which is not installed by us
 while true; do
-  cni_conf_name=$(ls "$HOST_CNI_NET_DIR" | grep -v antrea | head -n1)
+  # CNI conf file must have an extension of ".conflist", "*.conf", or "*.json".
+  cni_conf_name=$(ls "$HOST_CNI_NET_DIR" | grep -E "\.conflist$|\.conf$|\.json$" | grep -v antrea | head -n1)
   if [[ ! -z $cni_conf_name ]]; then
     break
   fi
@@ -69,6 +70,15 @@ cni_conf_sha=""
 function update_cni_conf {
     log_info "install_cni_chaining" "updating CNI conf file $cni_conf_name -> $cni_conf_name_antrea"
 
+    # The CNI conf file may not have been completely written.
+    while true; do
+        if [ -s "$cni_conf_path" ] && jq empty "$cni_conf_path" 2>/dev/null; then
+            break
+        fi
+        log_info "install_cni_chaining" "CNI conf file is empty or invalid. Retrying after 2 secs"
+        sleep 2s
+    done
+
     # We use the following steps:
     # 1. read the input file once and store its contents in a variable
     # 2. perform the necessary changes on the variable contents