refactor: only run systemctl when systemd is running as init

Based on reviewer feedback, changed the logic to only attempt
systemctl commands when systemd is actually running as PID 1
(has_systemd() returns true).

This is cleaner and more explicit:
- Systems with systemd running: use systemctl
- Systems with service command: use service
- Container environments: skip service management gracefully

The previous approach of running systemctl even when systemd
wasn't running was for image portability (container->VM), but
this is a niche use case.

Signed-off-by: Gajesh Bhat <gajeshbht@gmail.com>

Author: gajeshbhat

install.sh

@@ -310,25 +310,19 @@ start_docker_daemon() {
 	>&2 echo
 	>&2 echo "Starting and enabling Docker daemon service..."
 
-	# On modern RHEL/CentOS/Fedora systems, only systemctl exists (no 'service' command).
-	# In containers, 'systemctl start' fails but 'systemctl enable' succeeds, creating
-	# symlinks so Docker starts on boot when the system runs normally (outside container).
-	if command_exists systemctl; then
+	# Check if systemd is running as the init system
+	if has_systemd && command_exists systemctl; then
+		# systemd is running - use systemctl to start and enable the service
 		if ! is_dry_run; then
-			if has_systemd; then
-				>&2 echo "Using systemd to manage Docker service"
-			else
-				>&2 echo "Attempting to use systemctl (systemd not running as init)"
-			fi
+			>&2 echo "Using systemd to manage Docker service"
 		fi
 		(
 			set -x
-			# In containers, these commands may fail but we try anyway
-			$sh_c 'systemctl start docker' || true
-			$sh_c 'systemctl enable docker' || true
+			$sh_c 'systemctl start docker'
+			$sh_c 'systemctl enable docker'
 		)
 		if ! is_dry_run; then
-			>&2 echo "Docker service configuration attempted"
+			>&2 echo "Docker daemon started and enabled"
 		fi
 	elif command_exists service; then
 		# Fallback for older systems without systemd