Don't overwrite function on test environment

Instead of overwriting functions that use `exec fish` on test
environment, skip this call if the variable `CI` has been defined on the
running shell.

.travis.yml

@@ -20,7 +20,6 @@ env:
 
 before_install:
   - tools/travis_install_fish.sh
-  - fish -c 'ln -sf $TRAVIS_BUILD_DIR/tests/functions_override $fish_function_path[1]'
 
 before_script: pwd; tree -h
 

lib/refresh.fish

@@ -5,5 +5,5 @@
 #   Refresh (reload) the current fish session.
 
 function refresh -d "refresh the fish session"
-  exec fish < /dev/tty
+  set -q CI; or exec fish < /dev/tty
 end

pkg/omf/cli/omf.destroy.fish

@@ -20,5 +20,5 @@ function omf.destroy -d "Remove Oh My Fish"
     rm -rf "$OMF_PATH"
   end
 
-  exec fish < /dev/tty
+  set -q CI; or exec fish < /dev/tty
 end

tests/functions_override/refresh.fish

-# SYNOPSIS
-#   refresh
-#
-# OVERVIEW
-#   Refresh (reload) the current fish session.
-
-function refresh -d "refresh the fish session (Travis Override)"
-  echo !!! Shell refresh requested in testing Environment !!!
-  exit 0;
-end