kfdtest: Set XNACK mode according HSA_XNACK env setting

According env setting HSA_XNACK=1 or 0, set XNACK mode ON or OFF to run
KFDSVMRangeTest and KFDSVMEvictTest. If HSA_XNACK is not defined, use
system boot-time XNACK mode setting.

Restore to the original XNACK mode when test finished.

Change-Id: Ia896a1b0a90854646c8a79acca38a7d46098efde
Signed-off-by: Philip Yang <Philip.Yang@amd.com>

tests/kfdtest/src/KFDSVMRangeTest.cpp

@@ -36,6 +36,8 @@ void KFDSVMRangeTest::SetUp() {
 
     m_pIsaGen = IsaGenerator::Create(m_FamilyId);
 
+    SVMSetXNACKMode();
+
     ROUTINE_END
 }
 
@@ -46,6 +48,8 @@ void KFDSVMRangeTest::TearDown() {
         delete m_pIsaGen;
     m_pIsaGen = NULL;
 
+    SVMRestoreXNACKMode();
+
     KFDBaseComponentTest::TearDown();
 
     ROUTINE_END
@@ -1287,10 +1291,8 @@ TEST_F(KFDSVMRangeTest, ReadOnlyRangeTest) {
      */
     int pid = fork();
     if (pid == 0) {
-        if (hsaKmtOpenKFD() != HSAKMT_STATUS_SUCCESS) {
-            WARN() << "KFD open failed in child process" << std::endl;
-            exit(1);
-        }
+        TearDown();
+        SetUp();
     } else {
         int childStatus;