Lint on pkg/* packages

- pkg/useragent
- pkg/units
- pkg/ulimit
- pkg/truncindex
- pkg/timeoutconn
- pkg/term
- pkg/tarsum
- pkg/tailfile
- pkg/systemd
- pkg/stringutils
- pkg/stringid
- pkg/streamformatter
- pkg/sockets
- pkg/signal
- pkg/proxy
- pkg/progressreader
- pkg/pools
- pkg/plugins
- pkg/pidfile
- pkg/parsers
- pkg/parsers/filters
- pkg/parsers/kernel
- pkg/parsers/operatingsystem

Signed-off-by: Vincent Demeester <vincent@sbr.pm>

pidfile/pidfile_test.go

@@ -24,7 +24,7 @@ func TestNewAndRemove(t *testing.T) {
 }
 
 func TestRemoveInvalidPath(t *testing.T) {
-	file := PidFile{path: filepath.Join("foo", "bar")}
+	file := PIDFile{path: filepath.Join("foo", "bar")}
 
 	if err := file.Remove(); err == nil {
 		t.Fatal("Non-existing file doesn't give an error on delete")