Updated flux bootstrap to work with kairos-agent 2.8.15

flux/flux-bootstrap.sh

@@ -33,10 +33,12 @@ if flux version &>/dev/null; then
 fi
 
 # Determine what VCS we need to bootstrap
+# Starting in kairos  2.8.15, kairos-agent command returns empty string  instead of "null"
 for vcs in bitbucket_server git github gitlab; do
   # kairos-agent used to return `null` when a key wasn't set, now returns empty.
   # we handle both
-  if [[ $(kairos-agent config get flux.$vcs 2>/dev/null) != "" ]] && [[ $(kairos-agent config get flux.$vcs 2>/dev/null) != "null" ]]; then
+  value=$(kairos-agent config get flux.$vcs 2>/dev/null)
+  if [[ $value != "null" && -n $value ]]; then
     version_control=$vcs
     break
   fi
@@ -119,4 +121,4 @@ else
 fi
 
 error "Failed to bootstrap with Flux, timed out ($minutes minutes)"
-exit 4
+exit 4