Switch reboot default

In light of recent issues reported with soft reboot we are chaning the
reboot method to a full reboot. This is intended to reduce the number of
requests we receive to investigate boot issues.

Author: rjschwei

doc/adoc/user_guide.adoc

@@ -177,14 +177,13 @@ started. However, `kexec` is not supported and does not function in certain
 conditions. For example, the `run_migration` utility does not work in Xen
 based environments or when kernel keys change.
 +
-If kexec causes a kernel panic this can cause the system to hang and the
-distribution migration to fail. In that case refer to this TID:
-https://www.suse.com/support/kb/doc/?id=000019733
-And set the "soft_reboot" customization option:
+By default this method is disabled. Enabling soft reboot behavior via kexec
+requires an explicit configuration change by setting the "soft_reboot"
+customization option:
 +
 [listing]
 ----
-echo "soft_reboot: false" >> /etc/sle-migration-service.yml
+echo "soft_reboot: true" >> /etc/sle-migration-service.yml
 ----
 
 Option 2 - Trigger via reboot::
@@ -303,9 +302,10 @@ debug: true|false
 ----
 
 Configure Reboot Method::
-By default, the migration system uses `kexec` to boot back into the host
-system once migration is complete.  If this is in any way problematic,
-a regular `reboot` can be requested by setting `soft_reboot: false`.
+By default, the migration system uses a full reboot to boot back into the
+host system once migration is complete. It is possible to configure the
+migration system to use `kexec`, i.e. use a soft reboot by setting
+`soft_reboot: true` in the configuration. A soft reboot may trigger issues.
 +
 [listing]
 ----

suse_migration_services/migration_config.py

@@ -180,7 +180,7 @@ def is_zypper_migration_plugin_requested(self):
         return self.config_data.get('use_zypper_migration', True)
 
     def is_soft_reboot_requested(self):
-        return self.config_data.get('soft_reboot', True)
+        return self.config_data.get('soft_reboot', False)
 
     def is_host_independent_initd_requested(self):
         return self.config_data.get('build_host_independent_initrd', False)