utils: Add a simple testcase for osmo_hexdump

This code makes a simple dump and tests for the corner case
diff --git a/tests/testsuite.at b/tests/testsuite.at
index 59d660a..9124f25 100644
--- a/tests/testsuite.at
+++ b/tests/testsuite.at
@@ -118,6 +118,12 @@
 AT_CHECK([$abs_top_builddir/tests/gb/gprs_ns_test], [0], [expout], [ignore])
 AT_CLEANUP
 
+AT_SETUP([utils])
+AT_KEYWORDS([utils])
+cat $abs_srcdir/utils/utils_test.ok > expout
+AT_CHECK([$abs_top_builddir/tests/utils/utils_test], [0], [expout], [ignore])
+AT_CLEANUP
+
 AT_SETUP([bssgp-fc])
 AT_KEYWORDS([bssgp-fc])
 cat $abs_srcdir/gb/bssgp_fc_tests.ok > expout