Data Source Info suggests commands RRDTool can't honor

[netniV]

Describe the bug
There was a datasource with a number of issues most of which the tune sorted out. But it also showed, and still does, the following:

Required RRD step size is '60'
RRD maximum for Data Source 'traffic_in' should be 'NaN'
RRD maximum for Data Source 'traffic_out' should be 'NaN'
File RRA '0' has same CF/steps (AVERAGE, 1) as '1'
File RRA '1' has same CF/steps (AVERAGE, 1) as '0'
File RRA '9' has same CF/steps (MAX, 1) as '10'
File RRA '10' has same CF/steps (MAX, 1) as '9'
/usr/bin/rrdtool tune /usr/share/cacti/rra/501/10287.rrd --maximum traffic_in:NaN
/usr/bin/rrdtool tune /usr/share/cacti/rra/501/10287.rrd --maximum traffic_out:NaN

However, running the tune commands failed because RRDTool 1.6 does not support NaN as a valid value.

Expected behavior
The NaN should really be U

[cigamit]

Additionally, the Max values are being incorrectly calculated in some cases. One user reported an ifHighSpeed of 2000, and Cacti was recommending a maximum values of 1000.