[rancid] Cisco devices and calculating percent free

[Chris Wopat]

Looked into this a little further.

The disk space churn is being caused by this device type - Cisco
ASR920, with churn of whatever in bootflash:/tracelogs . IOS-XE seems
to be doing its own thing in there as files tend to be <1 day old
while no device changes are happening. The contents of this directory
are properly ignored and aren't in diffs, but this slight change in
disk space is causing the issue.

If I do comment this from rancid.types.conf or rancid.types.base, as
expected it removes the directory contents, which does contain
valuable info I like to have (ie which IOS images are chilling there):

#cisco;command;ios::DirSlotN;dir /all bootflash:

So, the only way for me to currently workaround this is to make a
change directly to rancid.pm, in "sub diskszsummary", such as, but not
limited to:

    #return("$total total ($pcnt% free)");
    return("$total total");

Certainly dirty but works. Curious if there's any thoughts on a
'clean' way to do this? I know there's an existing 'FILTER_OSC' flag
that I believe is intended to reduce churn in general, my best guess
for a 'clean' fix, if it makes sense to people, would be to check that
here and only return "$pcnt% free" if that isn't set.

My $.02

If people are opposed to such a thing, I'll likely add this to my
'manually patch these couple of things' list that already exists
post-upgrades.

Cheers
--Chris