tests: Only run one Machines test on VM instance without /dev/kvm

Each Machines test takes about 4 minutes with QEMU emulation, and they
are very prone to failing. Due to the automatic retry, the Machines
tests currently take about 6 hours on Fedora gating infrastructure, and
are just about impossible to get succeeding.

tests/run-test.sh

@@ -48,10 +48,16 @@ if [ -n "$test_optional" ]; then
     # TestUpdates: we can't run rebooting tests
     TESTS="$TESTS
          TestAutoUpdates
-         TestMachines
          TestStorage
          TestUpdates.testBasic
          TestUpdates.testSecurityOnly"
+
+    # Fedora gating tests are running on infra without /dev/kvm; Machines tests are too darn slow there
+    if [ -w /dev/kvm ]; then
+        TESTS="$TESTS TestMachines"
+    else
+        TESTS="$TESTS TestMachinesCreate.testCreateImportDisk"
+    fi
 fi
 
 if [ -n "$test_basic" ]; then