Make --postcopy flag mandatory with --postcopy-after-precopy

--postcopy-after-precopy is just an aditional flag for
postcopy migration.
Signed-off-by: NKothapally Madhu Pavan <kmp@linux.vnet.ibm.com>

tools/virsh-domain.c

@@ -10318,10 +10318,10 @@ cmdMigrate(vshControl *ctl, const vshCmd *cmd)
     }
 
     if (vshCommandOptBool(cmd, "postcopy-after-precopy")) {
-        if (!live_flag) {
+        if (!vshCommandOptBool(cmd, "postcopy")) {
             virReportError(VIR_ERR_ARGUMENT_UNSUPPORTED, "%s",
-                          _("post-copy migration is not supported with "
-                            "non-live or paused migration"));
+                          _("--postcopy-after-precopy can only be used with "
+                            "--postcopy"));
             goto cleanup;
         }
         iterEvent = virConnectDomainEventRegisterAny(

tools/virsh.pod

@@ -1617,8 +1617,8 @@ migration. I<--postcopy> enables post-copy logic in migration, but does not
 actually start post-copy, i.e., migration is started in pre-copy mode.
 Once migration is running, the user may switch to post-copy using the
 B<migrate-postcopy> command sent from another virsh instance or use
-I<--postcopy-after-precopy> to let libvirt automatically switch to
-post-copy after the first pass of pre-copy is finished.
+I<--postcopy-after-precopy> along with I<--postcopy> to let libvirt
+automatically switch to post-copy after the first pass of pre-copy is finished.
 
 I<--auto-converge> forces convergence during live migration. The initial
 guest CPU throttling rate can be set with I<auto-converge-initial>. If the