Extends .jscsrc to ignore 3rd party files

Adds a few files that should be skipped to the .jscsrc, since they are
beyond our control (external libs, generated coverage reports etc.)

This also reduces the error count to around 2k

Closes-Bug: 1463791
Change-Id: Iac87e41edd797c2a8318dcaceefe0651bd22dd61

.jscsrc

@@ -1,7 +1,11 @@
 {
   "excludeFiles": [
+    ".venv/**",
+    "bower_components/**",
+    "horizon/.coverage-karma/**",
+    "lib/**",
     "node_modules/**",
-    "bower_components/**"
+    "openstack_dashboard/.coverage-karma/**"
   ],
   "requireCurlyBraces": [
     "if",
@@ -51,4 +55,4 @@
   "disallowMultipleLineBreaks": true,
   "disallowTrailingComma": true,
   "requireParenthesesAroundIIFE": true
-}
+}