Bug#24624556: RDTIMESTAMPCOUNTER.TESTCYCLE UNIT TEST FAILS ON AARCH64.

The precision of the low-level ARM64 cycle timer varies
depending on implementation. Our current unit tests assumes
that the precision is low and therefore fails on some ARM64
machines. Remove this check from the unit test so that the
unit test passes on ARM64 regardless of precision.

Author: jhauglid

unittest/gunit/mysys_my_rdtsc-t.cc

@@ -113,9 +113,11 @@ TEST_F(RDTimeStampCounter, TestCycle)
   }
 
 #if defined(__aarch64__)
-  /* The ARM cycle timer has low resolution */
+  /*
+    The ARM cycle timer can have low resolution, so backward can be
+    0 or >0 depending on machine.
+  */
   EXPECT_EQ(LOOP_COUNT, nonzero);
-  EXPECT_NE(0, backward);
 #else
   /* Expect at most 1 backward, the cycle value can overflow */
   EXPECT_TRUE((backward <= 1)) << "The cycle timer is strictly increasing";