nsenter: stop option parsing on 1st non-option

"nsenter ls -l" gives: invalid option -- 'l'

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

util-linux/nsenter.c

@@ -103,8 +103,9 @@ static const struct namespace_descr ns_list[] = {
 };
 /*
  * Upstream nsenter doesn't support the short option for --preserve-credentials
+ * "+": stop on first non-option
  */
-static const char opt_str[] ALIGN1 = "U::i::u::n::p::m::""t:+S:+G:+r::w::F";
+static const char opt_str[] ALIGN1 = "+""U::i::u::n::p::m::""t:+S:+G:+r::w::F";
 
 #if ENABLE_LONG_OPTS
 static const char nsenter_longopts[] ALIGN1 =