[Performance] make auto-using faster.

Per https://github.com/creationix/nvm/issues/539#issuecomment-236830764

nvm.sh

@@ -2824,7 +2824,7 @@ nvm_auto() {
       nvm install >/dev/null
     fi
   elif [ "_$NVM_MODE" = '_use' ]; then
-    VERSION="$(nvm_alias default 2>/dev/null || nvm_echo)"
+   VERSION="$(nvm_resolve_local_alias default 2>/dev/null || nvm_echo)"
     if [ -n "$VERSION" ]; then
       nvm use --silent "$VERSION" >/dev/null
     elif nvm_rc_version >/dev/null 2>&1; then