Fix --force-handlers, and allow it in plays and ansible.cfg

The --force-handlers command line argument was not correctly running
handlers on hosts which had tasks that later failed. This corrects that,
and also allows you to specify force_handlers in ansible.cfg or in a
play.

test/integration/roles/test_force_handlers/handlers/main.yml

@@ -0,0 +1,2 @@
+- name: echoing handler
+  command: echo CALLED_HANDLER_{{ inventory_hostname }}

test/integration/roles/test_force_handlers/tasks/main.yml

@@ -0,0 +1,26 @@
+---
+
+# We notify for A and B, and hosts B and C fail.
+# When forcing, we expect A and B to run handlers
+# When not forcing, we expect only B to run handlers
+
+- name: notify the handler for host A and B
+  shell: echo
+  notify:
+    - echoing handler
+  when: inventory_hostname == 'A' or inventory_hostname == 'B'
+
+- name: fail task for all
+  fail: msg="Fail All"
+  when: fail_all is defined and fail_all
+
+- name: fail task for A
+  fail: msg="Fail A"
+  when: inventory_hostname == 'A'
+
+- name: fail task for C
+  fail: msg="Fail C"
+  when: inventory_hostname == 'C'
+  
+- name: echo after A and C have failed
+  command: echo CALLED_TASK_{{ inventory_hostname }}