Ignore swap (.swp) files in manifests folder

[dnoland1]

Describe the bug
I created a manifest in /var/lib/rancher/k3s/server/manifests/test.yaml and started k3s in server mode. Decided to edit the file using vi, which generates a .swp file in the same folder. This caused the following error message about every 15 seconds:

ERRO[2019-03-29T05:16:53.428115408Z] failed to process config: failed to process /var/lib/rancher/k3s/server/manifests/.test.yaml.swp: yaml: control characters are not allowed
ERRO[2019-03-29T05:17:08.429939965Z] failed to process config: failed to process /var/lib/rancher/k3s/server/manifests/.test.yaml.swp: yaml: control characters are not allowed

To Reproduce
See above

Expected behavior
Would be nice if .swp files were ignored. Not sure if it would make sense to have a whitelist of extensions like ".yml", ".yaml", etc. or a blacklist of extensions to ignore like ".swp", ".bak", etc.

Additional context
Discovered while testing #222

[deniseschannon]

We should do the reverse in look for only .yml, .yaml and .json only files.

[deniseschannon]

and ignore any files that start with .

[dnoland1]

Tested on v0.5.0-rc3 (21a9dbe). Successfully deployed files named test.yaml and test.yml by placing in /var/lib/rancher/k3s/server/manifests. Confirmed files with .swp and .txt were ignored. .test.yml was also ignored. Working as expected, closing issue.