Sub-tests in ubuntu_kvm_unit_tests timeout on Openstack s390x with X-4.4

This issue is not a regression as we switched to a full test for security respins in this cycle.

Almost all of the sub-tests are failing on Openstack s390x with timeout:
* cmm
* cpumodel
* css
* diag10
* diag288
* diag308
* edat
* emulator
* epsw
* gs
* iep
* intercept
* mvpg
* mvpg-sie
* pfmf
* sck
* sclp-1g
* sclp-3g
* selftest-setup
* sie
* sieve
* skey
* skrf
* smp
* spec_ex-sie
* sthyi
* stsi
* tprot
* uv-guest
* vector

Except the following two being skipped:
 * panic-loop-extint
 * panic-loop-pgm

Test log (taking cmm for example):
 Running '/home/ubuntu/autotest/client/tmp/ubuntu_kvm_unit_tests/src/kvm-unit-tests/tests/cmm'
 BUILD_HEAD=6a7ccca1
 timeout -k 1s --foreground 90s /usr/bin/qemu-system-s390x -nodefaults -nographic -machine s390-ccw-virtio,accel=kvm -chardev stdio,id=con0 -device sclpconsole,chardev=con0 -kernel /tmp/tmp.fl3C5bz7Tx -smp 1 qemu-system-s390x: terminating on signal 15 from pid 10247
 FAIL cmm (timeout; duration=90s)

Please find attachment for the complete test log.