Repeated Error Messages if Python not installed on SSH host

We spam the error message multiple times.

The simplest solution to this is likely to only attempt to fill `_platform_info` once via `_init_remote_platform_info` (e.g. `_platform_info['attempted']=True`)

Perhaps setting a dummy key will prevent this from being displayed so many times.

```
>>> s=ssh('root', 'device')
[x] Connecting to localhost on port 11022
[+] Connecting to localhost on port 11022: Done
[ERROR] python is not installed on the remote system 'localhost'
[ERROR] python is not installed on the remote system 'localhost'
[ERROR] python is not installed on the remote system 'localhost'
[ERROR] python is not installed on the remote system 'localhost'
[ERROR] python is not installed on the remote system 'localhost'
[ERROR] python is not installed on the remote system 'localhost'
[!] Only Linux is supported for ASLR checks.
[ERROR] python is not installed on the remote system 'localhost'
[ERROR] python is not installed on the remote system 'localhost'
[ERROR] python is not installed on the remote system 'localhost'
[*] root@localhost:
Distro Unknown Unknown
OS: Unknown
Arch: Unknown
Version: 0.0.0
ASLR: Disabled
Note: Susceptible to ASLR ulimit trick (CVE-2016-3672)
```