SLES grain fix (#3275)

The 'os' grain in SLES 11 SP2 is 'SUSE  Enterprise Server' (two spaces).
Tried to fix this a couple days ago but didn't notice the extra space
after 'SUSE'. See the following:

https://github.com/saltstack/salt/issues/3275#issuecomment-12425372
Replace hardcoded python executable with sys.executable
Add missing space to log message

When testing a new virtualenv installation today, I noticed the
following log message:

[INFO    ] Authentication failed from host foo, the key is in pending
and needs to be accepted with salt-key-a foo

This commit adds a space between "salt-key" and "-a".