qemuMigrationDstPrepareAny: Don't overwrite error in cleanup path

There are several functions called in the cleanup path. Some of
them do report error (e.g. qemuDomainRemoveInactiveJob()) which
may result in overwriting an error reported earlier with some
less useful message.
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>
Reviewed-by: NJiri Denemark <jdenemar@redhat.com>

src/qemu/qemu_migration.c

@@ -2282,6 +2282,7 @@ qemuMigrationDstPrepareAny(virQEMUDriverPtr driver,
 {
     virDomainObjPtr vm = NULL;
     virObjectEventPtr event = NULL;
+    virErrorPtr origErr;
     int ret = -1;
     int dataFD[2] = { -1, -1 };
     qemuDomainObjPrivatePtr priv = NULL;
@@ -2595,6 +2596,7 @@ qemuMigrationDstPrepareAny(virQEMUDriverPtr driver,
     ret = 0;
 
  cleanup:
+    virErrorPreserveLast(&origErr);
     VIR_FREE(tlsAlias);
     qemuProcessIncomingDefFree(incoming);
     VIR_FREE(xmlout);
@@ -2618,6 +2620,7 @@ qemuMigrationDstPrepareAny(virQEMUDriverPtr driver,
     qemuMigrationCookieFree(mig);
     virObjectUnref(caps);
     virNWFilterUnlockFilterUpdates();
+    virErrorRestore(&origErr);
     return ret;
 
  stopjob: