Remove delete ghost migrations option

I dont know whose idea was to use delete ghost migrations but it was a
terrible one. We never simply delete migrations in our development and
removing them means a downgrade happened which will cause even more
trouble when we try to reapply them (because they are not there in the
first place anymore)

Ticket:	#15774
Ticket:	#15832

gui/tools/backup.py

@@ -746,7 +746,6 @@ def run(self):
                         '/usr/local/www/freenasUI/manage.py',
                         'migrate',
                         '--merge',
-                        '--delete-ghost-migrations'
                 ], stdout=devnull, stderr=devnull) != 0:
                     self.fail('Could not restore database')
                     return

src/freenas-installer/etc/install.sh

@@ -1031,7 +1031,7 @@ menu_install()
 	# This should be investigated.
 #	chroot /tmp/data /bin/sh -c "/usr/bin/yes | \
 #		/usr/local/bin/python
-#		      /usr/local/www/freenasUI/manage.py migrate --all --merge --delete-ghost-migrations"
+#		      /usr/local/www/freenasUI/manage.py migrate --all --merge"
 	# Create upgrade sentinel files
 	: > /tmp/data/${CD_UPGRADE_SENTINEL}
 	: > /tmp/data/${NEED_UPDATE_SENTINEL}

src/freenas/etc/ix.rc.d/ix-update

@@ -45,7 +45,7 @@ db_update_real()
 
 	touch /tmp/.sqlite3_ha_skip
 	yes | /usr/local/bin/python \
-	    /usr/local/www/freenasUI/manage.py migrate --merge --delete-ghost-migrations > \
+	    /usr/local/www/freenasUI/manage.py migrate --merge > \
 		$UPDATE_FAILED_LOG 2>&1
 	if [ $? -ne 0 ]; then
 		rm -f /tmp/.sqlite3_ha_skip