qemu: Don't reset "events" migration capability

When creating v3.2.0-77-g8be3ccd0 commit, I completely forgot that one
migration capability is very special. It's the "events" capability which
tells QEMU to report "MIGRATION" events. Since libvirt always wants the
events, it is enabled in qemuConnectMonitor and the rest of the code
should not touch it.

https://bugzilla.redhat.com/show_bug.cgi?id=1439841
https://bugzilla.redhat.com/show_bug.cgi?id=1441165Messed-up-by: NJiri Denemark <jdenemar@redhat.com>
Signed-off-by: NJiri Denemark <jdenemar@redhat.com>

src/qemu/qemu_migration.c

@@ -5919,6 +5919,11 @@ qemuMigrationReset(virQEMUDriverPtr driver,
         goto cleanup;
 
     for (cap = 0; cap < QEMU_MONITOR_MIGRATION_CAPS_LAST; cap++) {
+        /* "events" capability is set (when supported) in qemuConnectMonitor
+         * and should never be cleared */
+        if (cap == QEMU_MONITOR_MIGRATION_CAPS_EVENTS)
+            continue;
+
         if (qemuMigrationSetOption(driver, vm, cap, false, job) < 0)
             goto cleanup;
     }