cli/bash-completion: normalize OPTIONS_TYPE to use it inside _nmcli_compl_ARGS()

Later _nmcli_compl_ARGS() wants to check $OPTIONS_TYPE to behave differently
depending on the type. As we accept abbreviations of $OPTIONS_TYPE, let's normalize
the value, so that we don't have to consider abbrevations later on.

Signed-off-by: Thomas Haller <thaller@redhat.com>
dispatcher: fix crash on missing scripts (bgo #738654)

GLib-CRITICAL **: g_variant_type_checked_: assertion `g_variant_type_string_is_valid (type_string)' failed
GLib-CRITICAL **: g_variant_new_array: assertion `n_children > 0 || child_type != NULL' failed

https://bugzilla.gnome.org/show_bug.cgi?id=738654