fix addition of empty newline to end of known_hosts

when cleaning the known_hosts file we are adding a newline to the
end of the file, since the scanner returns the lines without '\n'
character we are adding it to properly recreate the  known_hosts
file, but this ends up adding an extra newline at the end of the
file

this commit changes the splitFunc for bufio.Scanner which returns
the lines with the '\n' character so that we don't have to add it
so the extra newline at the end of the file is not added

the splitFunc is a modified version of the ScanLines function from
the bufio package with the change to return lines along with '\n'

pkg/crc/ssh/keys.go

@@ -2,6 +2,7 @@ package ssh
 
 import (
 	"bufio"
+	"bytes"
 	"crypto/ecdsa"
 	"crypto/elliptic"
 	"crypto/rand"
@@ -98,15 +99,30 @@ func RemoveCRCHostEntriesFromKnownHosts() error {
 		return fmt.Errorf("Error trying to change permissions for temp file: %w", err)
 	}
 
+	// return each line along with the newline '\n' marker
+	var splitFunc = func(data []byte, atEOF bool) (advance int, token []byte, err error) {
+		if atEOF && len(data) == 0 {
+			return 0, nil, nil
+		}
+		if i := bytes.IndexByte(data, '\n'); i >= 0 {
+			return i + 1, data[0 : i+1], nil
+		}
+		if atEOF {
+			return len(data), data, nil
+		}
+		return 0, nil, nil
+	}
+
 	var foundCRCEntries bool
 	scanner := bufio.NewScanner(f)
+	scanner.Split(splitFunc)
 	writer := bufio.NewWriter(tempHostsFile)
 	for scanner.Scan() {
 		if strings.Contains(scanner.Text(), "[127.0.0.1]:2222") || strings.Contains(scanner.Text(), "192.168.130.11") {
 			foundCRCEntries = true
 			continue
 		}
-		if _, err := writer.WriteString(fmt.Sprintf("%s\n", scanner.Text())); err != nil {
+		if _, err := writer.WriteString(scanner.Text()); err != nil {
 			return fmt.Errorf("Error while writing hostsfile content to temp file: %w", err)
 		}
 	}