res_pjsip_outbound_registration: registration stops due to fatal 4xx response

During outbound registration it is possible to receive a fatal (any permanent/
non-temporary 4xx, 5xx, 6xx) response from the registrar that is simply due
to a problem with the registrar itself. Upon receiving the failure response
Asterisk terminates outbound registration for the given endpoint.

This patch adds an option, 'fatal_retry_interval', that when set continues
outbound registration at the given interval up to 'max_retries' upon receiving
a fatal response.

ASTERISK-25485 #close

Change-Id: Ibc2c7b47164ac89cc803433c0bbe7063bfa143a2

contrib/ast-db-manage/config/versions/28ce1e718f05_add_fatal_response_interval.py

@@ -0,0 +1,22 @@
+"""add fatal_response_interval
+
+Revision ID: 28ce1e718f05
+Revises: 154177371065
+Create Date: 2015-10-20 17:57:45.560585
+
+"""
+
+# revision identifiers, used by Alembic.
+revision = '28ce1e718f05'
+down_revision = '154177371065'
+
+from alembic import op
+import sqlalchemy as sa
+
+
+def upgrade():
+    op.add_column('ps_registrations', sa.Column('fatal_retry_interval', sa.Integer))
+
+
+def downgrade():
+    op.drop_column('ps_registrations', 'fatal_retry_interval')