[sanboot] Extend the "keep-san" option to non-iSCSI SAN protocols

This disgustingly ugly hack just keeps getting worse.

src/arch/i386/interface/pcbios/keepsan.c

@@ -0,0 +1,26 @@
+#include <stdint.h>
+#include <stdio.h>
+#include <gpxe/settings.h>
+#include <gpxe/dhcp.h>
+#include <gpxe/init.h>
+#include <gpxe/sanboot.h>
+#include <usr/autoboot.h>
+
+struct setting keep_san_setting __setting = {
+	.name = "keep-san",
+	.description = "Preserve SAN connection",
+	.tag = DHCP_EB_KEEP_SAN,
+	.type = &setting_type_int8,
+};
+
+int keep_san ( void ) {
+	int keep_san;
+
+	keep_san = fetch_intz_setting ( NULL, &keep_san_setting );
+	if ( ! keep_san )
+		return 0;
+
+	printf ( "Preserving connection to SAN disk\n" );
+	shutdown_exit_flags |= SHUTDOWN_KEEP_DEVICES;
+	return 1;
+}