pty04 from pty in ubuntu_ltp failed on B-AWS-4.15 with ARM64 instance a1.medium

Issue found on B-AWS-4.15 (4.15.0-1066.70) ARM64 instance a1.medium only (passed on the rest)

 startup='Fri Apr 10 10:18:23 2020'
 tst_test.c:1241: INFO: Timeout per run is 0h 05m 00s
 pty04.c:95: INFO: PTS path is /dev/pts/0
 pty04.c:149: INFO: Netdev is sl0
 pty04.c:158: INFO: Netdev MTU is 8192 (we set 8192)
 pty04.c:175: INFO: Bound netdev 2274 to socket 23
 pty04.c:123: PASS: Wrote PTY 1
 pty04.c:133: PASS: Wrote PTY 2
 pty04.c:208: INFO: Reading from socket 23
 safe_macros.c:260: BROK: pty04.c:210: read(23,0xaaaaccbbea30,8191) failed, returned 90: SUCCESS (0)
 tst_test.c:368: BROK: Reported by child (5562)
 pty04.c:138: PASS: Writing to PTY interrupted by hangup
 tst_checkpoint.c:149: BROK: pty04.c:248: tst_checkpoint_wait(0, 10000): ETIMEDOUT (110)
 tst_test.c:368: WARN: Reported by child (5564)

 Summary:
 passed 3
 failed 0
 skipped 0
 warnings 1
 tag=pty04 stime=1586513903 dur=10 exit=exited stat=6 core=no cu=0 cs=0