Make Continuous installer continuous only during execution phase

`common.Continuous` class is a basis for uninstallers, which should execute
all the steps regardless of occuring errors. However, we would like the
installer to raise exceptions and return non-zero exit code during validation
phase when some preconditions are not met.

Add a separate exception handler which catches exceptions and logs them as
errors during execution phase only.

https://fedorahosted.org/freeipa/ticket/5725

Reviewed-By: Petr Spacek <pspacek@redhat.com>

ipapython/install/common.py

@@ -86,9 +86,9 @@ class Interactive(core.Configurable):
 
 
 class Continuous(core.Configurable):
-    def _handle_exception(self, exc_info):
+    def _handle_execute_exception(self, exc_info):
         try:
-            super(Continuous, self)._handle_exception(exc_info)
+            super(Continuous, self)._handle_execute_exception(exc_info)
         except BaseException as e:
             self.log.debug(traceback.format_exc())
             if isinstance(e, Exception):

ipapython/install/core.py

@@ -375,11 +375,8 @@ class Configurable(six.with_metaclass(abc.ABCMeta, object)):
                 try:
                     exc_handler(exc_info)
                 except BaseException:
-                    raise
-                else:
-                    break
-                finally:
                     self.__transition(running_state, _FAILED)
+                    raise
 
             if self.__state != running_state:
                 break