Check whether client NetworkRequest includes a valid specifier

L2capNetworkSpecifier matching semantics ensure that if the specifier is
not null, it must be an L2capNetworkSpecifier.

This change ensures onNetworkNeeded() filters out all null specifiers
as well as L2capNetworkSpecifiers that are considered to be invalid for
client networks.

Test: TH
Change-Id: I515d6b606bb5e05d57edb5753480f479f49dc54e
1 file changed