Avoid storing non-positive satellite data usage

The computePerAppSatelliteDataUsageWithSession method could store
per-app data usage values that were less than or equal to zero. This
could lead to unnecessary or incorrect data being stored in the
satellite session usage map.

This change introduces a check to ensure that only data usage values
greater than zero are added to the map.

Flag: EXEMPT BugFix
Bug: 440454348
Test: m and atest
Change-Id: Ieabfb5822637552ab32ac05771a1e981cfbb0a8b