When creating RRD File, more data sources than expected may be defined

[TheWitness]

Describe the bug

So, when you create a Data Template that includes Data Sources for multiple Data Query Graph Templates, Cacti accidentally creates the RRDfile with all the Data Sources included. This leads to much larger RRDfiles that you would expect. In large environments this can be a problem.

To Reproduce

Steps to reproduce the behavior:

1. Create a Data Template like below:

2. In the example, there are three load average Data Sources that will go on one Graph and two each paired for another Graph as shown below:

3. However, when you dump the resulting RRDfiles, you get this:

[root@vmhost3 ~]# rrdtool fetch /var/www/html/cacti/rra/1/13/9/2305.rrd LAST | more
                   Device_Reads       Bytes_Written       Device_Writes        1Min_LoadAvg        5Min_LoadAvg       15Min_LoadAvg          Bytes_Read

1667664000: -nan 0.0000000000e+00 -nan -nan -nan -nan 0.0000000000e+00
1667664900: -nan 0.0000000000e+00 -nan -nan -nan -nan 0.0000000000e+00
1667665800: -nan 0.0000000000e+00 -nan -nan -nan -nan 0.0000000000e+00
1667666700: -nan 0.0000000000e+00 -nan -nan -nan -nan 0.0000000000e+00
1667667600: -nan 0.0000000000e+00 -nan -nan -nan -nan 0.0000000000e+00
1667668500: -nan 0.0000000000e+00 -nan -nan -nan -nan 0.0000000000e+00
1667669400: -nan 0.0000000000e+00 -nan -nan -nan -nan 0.0000000000e+00
1667670300: -nan 0.0000000000e+00 -nan -nan -nan -nan 0.0000000000e+00
1667671200: -nan 0.0000000000e+00 -nan -nan -nan -nan 0.0000000000e+00
1667672100: -nan 0.0000000000e+00 -nan -nan -nan -nan 0.0000000000e+00
1667673000: -nan 0.0000000000e+00 -nan -nan -nan -nan 0.0000000000e+00
1667673900: -nan 0.0000000000e+00 -nan -nan -nan -nan 0.0000000000e+00
1667674800: -nan 0.0000000000e+00 -nan -nan -nan -nan 0.0000000000e+00
1667675700: -nan 0.0000000000e+00 -nan -nan -nan -nan 0.0000000000e+00
1667676600: -nan 0.0000000000e+00 -nan -nan -nan -nan 0.0000000000e+00
1667677500: -nan 0.0000000000e+00 -nan -nan -nan -nan 0.0000000000e+00
1667678400: -nan 0.0000000000e+00 -nan -nan -nan -nan 0.0000000000e+00
1667679300: -nan 0.0000000000e+00 -nan -nan -nan -nan 0.0000000000e+00
1667680200: -nan 0.0000000000e+00 -nan -nan -nan -nan 0.0000000000e+00

The most important thing is all the NAN's. This specific Data Source is for the Device Read/Writes graph template, and you can see that all the other Data Sources are included in this Data Source resulting in wasted space in the RRDfile.

Expected behavior

Cacti should only create the used Data Sources from the Data Template as associated with the specific Graph.