Bug 1016885 - Send a notification instead of displaying the dialer when receiving an unsolicited USSD notification r=etienne

(cherry picked from commit ddbf0e11b494fd9665545141485d0b70cab6d514)

Conflicts:
	apps/communications/dialer/js/dialer.js
	apps/communications/dialer/js/mmi.js
	apps/communications/dialer/test/unit/dialer_test.js
Bug 1016885 - Always initialize the MmiManager before sending a notification r=etienne

(cherry picked from commit c664153cd702ae1db12a485e539bae88b9bdcdea)

Conflicts:
	apps/communications/dialer/test/unit/mmi_test.js
Merge pull request #21476 from gabrielesvelto/bug-1016885-v1.4-uplift

Bug 1016885 - v1.4 uplift