Cherry-pick #15945 to 7.x: remove debug logging from streambuf (#15971)

(cherry picked from commit f465204)

libbeat/common/streambuf/streambuf.go

@@ -35,8 +35,6 @@ package streambuf
 import (
 	"bytes"
 	"errors"
-
-	"github.com/elastic/beats/libbeat/logp"
 )
 
 // Error returned if Append or Write operation is not allowed due to the buffer
@@ -231,11 +229,7 @@ func (b *Buffer) Advance(count int) error {
 // Failed returns true if buffer is in failed state. If buffer is in failed
 // state, almost all buffer operations will fail
 func (b *Buffer) Failed() bool {
-	failed := b.err != nil
-	if failed {
-		logp.Debug("streambuf", "buf parser already failed with: %s", b.err)
-	}
-	return failed
+	return b.err != nil
 }
 
 // Err returns the error value of the last failed operation.