Earlier versions of RRDTool do not correctly ignore previous updates #4321
Description
Describe the bug
RRDtool versions less than 1.5 do not have the 'skip' option to silently ignore previous updates. This can cause a gap in graphs somewhat randomly.
To Reproduce
It's not easy to reproduce, but in Cacti 1.2.17, we/I inadvertently removed the Data Source locking function that prevented this type of behavior. Though we recommend you get off old RRDtool version 1.4 and earlier versions, we will make a fix to re-introduce that locking functionality.
Expected behavior
Cacti needs to work.