Add tests for server/config.go

The tests are trying to read an write configuration files and check that the
fields are being set or saved properly.

A folder fixtures/ was created on server/ as well adding an example crio.conf
file to it.

Note: some extra paths about Vagrant and VSCode were added to gitignore.
Signed-off-by: Álex González <agonzalezro@gmail.com>

server/fixtures/crio.conf

@@ -0,0 +1,41 @@
+[crio]
+root = "/var/lib/containers/storage"
+runroot = "/var/run/containers/storage"
+storage_driver = "overlay"
+storage_option = ["overlay.override_kernel_check=1"]
+
+[crio.api]
+listen = "/var/run/crio.sock"
+stream_address = "localhost"
+stream_port = "10010"
+
+[crio.runtime]
+runtime = "/usr/local/bin/runc"
+runtime_untrusted_workload = "untrusted"
+default_workload_trust = "trusted"
+conmon = "/usr/local/libexec/crio/conmon"
+conmon_env = [
+	"PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin",
+]
+selinux = true
+seccomp_profile = "/etc/crio/seccomp.json"
+apparmor_profile = "crio-default"
+cgroup_manager = "cgroupfs"
+pids_limit = 1024
+
+[crio.image]
+default_transport = "docker://"
+pause_image = "kubernetes/pause"
+pause_command = "/pause"
+signature_policy = "/tmp"
+image_volumes = "mkdir"
+insecure_registries = [
+	"insecure-registry:1234",
+]
+registries = [
+	"registry:4321",
+]
+
+[crio.network]
+network_dir = "/etc/cni/net.d/"
+plugin_dir = "/opt/cni/bin/"