Tests "v3 client message" and "v3 sub" fail on arm

[mattst88]

Downstream report: https://bugs.gentoo.org/746929

The "v3 client message" and "v3 sub" tests fail on arm (but pass on aarch64 and amd64).

./persist_read_test


     CUnit - A unit testing framework for C - Version 2.1-3
     http://cunit.sourceforge.net/


Suite: Persist read
  Test: Persistence disabled ...passed
  Test: Empty file ...passed
  Test: Corrupt header ...passed
  Test: Unsupported version ...passed
  Test: v3 config ok ...passed
  Test: v3 config bad truncated ...passed
  Test: v3 config bad dbid ...passed
  Test: v3 bad chunk ...passed
  Test: v3 message store ...passed
  Test: v3 client ...passed
  Test: v3 client message ...FAILED
    1. persist_read_test.c:273  - CU_ASSERT_PTR_NOT_NULL(context->msgs_out.inflight)
  Test: v3 retain ...passed
  Test: v3 sub ...FAILED
    1. persist_read_test.c:367  - CU_ASSERT_PTR_NOT_NULL(last_sub)
    2. persist_read_test.c:372  - CU_ASSERT_EQUAL(last_qos,1)
  Test: v4 config ok ...passed
  Test: v4 message store ...passed
  Test: v5 client ...passed
  Test: v5 config bad truncated ...passed
  Test: v5 bad chunk ...passed
  Test: v6 config ok ...passed
  Test: v6 message store ...passed
  Test: v6 message store+props ...passed
  Test: v6 client ...passed
  Test: v6 client message ...passed
  Test: v6 client message+props ...passed
  Test: v6 retain ...passed
  Test: v6 sub ...passed

Run Summary:    Type  Total    Ran Passed Failed Inactive
              suites      1      1    n/a      0        0
               tests     26     26     24      2        0
             asserts    192    192    189      3      n/a

Elapsed time =    0.003 seconds```