Fix jvmnativestest test_EnsureWallClockTime()

[keithc-ca]

Fixes: #11293.

[keithc-ca]

Jenkins test sanity aix,osx,plinux,win32 jdk8

[pshipton]

Grinders can handle the testing. The test isn't enabled on jdk8 for some reason, tested jdk11.

AIX - https://openj9-jenkins.osuosl.org/view/Test/job/Grinder/377
OSX - https://openj9-jenkins.osuosl.org/view/Test/job/Grinder/378
plinux - https://openj9-jenkins.osuosl.org/view/Test/job/Grinder/379
zlinux - https://openj9-jenkins.osuosl.org/view/Test/job/Grinder/380
win - https://openj9-jenkins.osuosl.org/view/Test/job/Grinder/381

[pshipton]

There aren't any OSX machines available atm, but all other platforms passed. I'll assume OSX won't be a problem.

[keithc-ca]

The implementation of omrtime_current_time_nanos() is different on OSX, but not enough so to be concerned that we'll see failures there.

[pshipton]

I'll check the grinder later.

[pshipton]

The OSX grinder did pass.

[pshipton]

I'm going to revert this. In PR testing for #13899, jvmnativestest_0 failed twice, both on zlinux.