Feature: Don't display redundant error messages on execute failure

Showing the same error in three different ways seems redundant. Is it possible to collapse into one?

The second one looks most relevant.

```
cap aborted!
SSHKit::Runner::ExecuteError: Exception while executing on host 12.34.56.78: Exception while executing on host 12.34.56.78: logrotate -f /etc/logrotate.conf exit status: 1
logrotate -f /etc/logrotate.conf stdout: Nothing written
logrotate -f /etc/logrotate.conf stderr: error: error running non-shared postrotate script for /path/to/log1.log of '/path/to/log1.log
/path/to/log2.log
'

SSHKit::Runner::ExecuteError: Exception while executing on host 12.34.56.78: logrotate -f /etc/logrotate.conf exit status: 1
logrotate -f /etc/logrotate.conf stdout: Nothing written
logrotate -f /etc/logrotate.conf stderr: error: error running non-shared postrotate script for /path/to/log1.log of '/path/to/log1.log
/path/to/log2.log
'

SSHKit::Command::Failed: logrotate -f /etc/logrotate.conf exit status: 1
logrotate -f /etc/logrotate.conf stdout: Nothing written
logrotate -f /etc/logrotate.conf stderr: error: error running non-shared postrotate script for /path/to/log1.log of '/root/apps/eme/shared/log/staging.log
/path/to/log2.log
'
```

Background: It occurred when I run

``` ruby
execute 'logrotate -f /etc/logrotate.conf'
```

on a single server, where the `postrotate` script for logrotate exits with a failure status.