Remove BarringInfo#isServiceBarred()

Address API Council comments:
-Remove convenience method isServiceBarred()
-Pre-construct default barring objects rather than
 construct new ones in case the struct is sparsely
 populated.

Bug: 148553656
Test: atest BarringInfoTest
Change-Id: Ib0cbdfb431e1fc57afe16595406e0a4d70af8945