Add retry on file rename

We use os.Rename to avoid potentially creating a situation where a
config file might be corrupted. This can however lead to a weird
situation when another process locks the file (i.e. Antivirus). Adding a
short retry loop should allow us to wait until the other process is
done.

[#172734111](https://www.pivotaltracker.com/story/show/172734111)

Co-authored-by: Sebastian Vidrio <svidrio@vmware.com>

util/configv3/write_config.go

@@ -6,6 +6,7 @@ import (
 	"os"
 	"os/signal"
 	"syscall"
+	"time"
 )
 
 // WriteConfig creates the .cf directory and then writes the config.json. The
@@ -44,6 +45,14 @@ func (c *Config) WriteConfig() error {
 		return err
 	}
 
+	for i := 0; i < 5; i++ {
+		if err := os.Rename(tempConfigFileName, ConfigFilePath()); err == nil {
+			return nil
+		}
+
+		time.Sleep(50 * time.Millisecond)
+	}
+
 	return os.Rename(tempConfigFileName, ConfigFilePath())
 }