tests: avoid false ulimit failure on some systems

* tests/misc/cut-huge-range.sh: On some systems returns_ may
use more memory, so incorporate that in the determination
of the ulimit value to use.  Noticed on ARMv7 with bash-4.4.12,
and x86_64 with bash-4.2.37.
Fixes http://bugs.gnu.org/26253

tests/misc/cut-huge-range.sh

@@ -20,9 +20,8 @@
 print_ver_ cut
 getlimits_
 
-vm=$(get_min_ulimit_v_ cut -b1 /dev/null) \
+vm=$(get_min_ulimit_v_ returns_ 0 cut -b1 /dev/null) \
   || skip_ "this shell lacks ulimit support"
-vm=$(($vm + 1000)) # avoid spurious failures
 
 # sed script to subtract one from the input.
 # Each input line should consist of a positive decimal number.