Add support for GitPython and salt-ssh on FreeBSD masters

This change tweaks the GitPython package installation state to support
alternate package names (on FreeBSD, it's called "py27-GitPython").
Also, on FreeBSD salt-ssh is included in the "py27-salt" package by
default, requiring an update to `distro_map`.

salt/gitfs/gitpython.sls

@@ -8,6 +8,7 @@ GitPython:
 {% else %}
 
 python-git:
-  pkg.installed
+  pkg.installed:
+    - name: {{ salt_settings['python_git'] }}
 
 {% endif %}