Fix starting skillstest via start-mycroft.sh

This also removes the ability to pass the skills dir as the first argument. Instead this was moved to an environment variable called SKILLS_DIR to prevent conflict with pytest arguments

test/integrationtests/skills/discover_tests.py

@@ -17,7 +17,6 @@ import pytest
 import glob
 import os
 from os.path import exists, join, expanduser
-import sys
 import imp
 
 from mycroft.configuration import Configuration
@@ -64,11 +63,13 @@ def discover_tests(skills_dir):
 
 
 def get_skills_dir():
-    if len(sys.argv) > 1:
-        return expanduser(sys.argv[-1])
-
-    return expanduser(join(Configuration.get()['data_dir'],
-                      Configuration.get()['skills']['msm']['directory']))
+    return (
+        expanduser(os.environ.get('SKILLS_DIR', '')) or
+        expanduser(join(
+            Configuration.get()['data_dir'],
+            Configuration.get()['skills']['msm']['directory']
+        ))
+    )
 
 
 skills_dir = get_skills_dir()