Bluedroid: Update PBAP Filter logic to avoid loss of fields.

In PBAP there are filters for unsupported fields. But the logic
to check these has issue. It checks for Attribute string holds
unsupported parameter, rather than begins with.  So if the
field data has pattern matching unsupported field, that complete
attribute are being removed. The current logic fixes the issue.

Change-Id: Iafcc2915a81e3847f7bfe435a3329b708980af6e
CRs-Fixed: 509165