Fix basedir check and parent dir extraction in filecount input

[danielnelson]

Not just a Windows bug, previously we would panic on paths without a /, and it was possible to not detect the top directory if it was aliased with a different path.

closes #5621

Required for all PRs:

• Signed CLA.
• Associated README.md updated.
• Has appropriate unit tests.

[SimonMcN]

This does not work for me on windows, was the fix tested on windows, or just linux please ?
2019-07-02T13:32:03Z I! Loaded inputs: filecount win_services win_perf_counters
2019-07-02T13:32:03Z I! Loaded aggregators:
2019-07-02T13:32:03Z I! Loaded processors:
2019-07-02T13:32:03Z I! Loaded outputs: influxdb
2019-07-02T13:32:03Z I! Tags enabled: ENV=PROD host=DLS07-P
2019-07-02T13:32:03Z I! [agent] Config: Interval:10s, Quiet:false, Hostname:"DLS07-P", Flush Interval:10s
2019-07-02T13:32:58Z I! [agent] Hang on, flushing any cached metrics before shutdown

tested with:
C:\telegraf\telegraf.exe --config c:\telegraf\prod.conf --config-directory c:\telegraf\conf.d --test --debug

[[inputs.filecount]]
directories = ["E:/mydirectory/processed/Failed"]
name = "*"
recursive = true
regular_only = true
size = "0B"
mtime = "0s"

[SimonMcN]

telegraf.exe V1.11.0

[danielnelson]

@SimonMcN Most likely I only tested on Linux, I'll reopen the issue and try it out when I have a Windows system available.

[SimonMcN]

I'd appreciate it. I know the Linux and windows filesystems have different mount point syntax so it would be easy to break it by mistake..... Either that or I am incapable 🤔😐😋

[danielnelson]

Looks to be related to the path separators, I believe using backslashes will workaround this issue until the fix is released. You can either escape the backslashes \\ or use single quote "literal" strings:

directories = ['E:\mydirectory\processed\Failed']

[danielnelson]

Fix for the separator issue is here: #6077