[MS17.2] Fix remaining daily budget assertion

Currently, the test didn't mock data usage of the month.
Thus, when asserting remaining budget, the calculation
always assumes there is no used data, hence wrong budget
value is expected. See #getRemainingDailyBudget.

This change makes data usage of this month includes the
bytes used today. And adjust the policy limit accordingly.

Test: atest MultipathPolicyTrackerTest
Bug: 204830222
Change-Id: I3ca6505f8d502047485ba3676f16fbc474117cc1
1 file changed