binder: libbinder_tls ensure to check trigger at least once.

If the SSL_write / SSL_read finishes in one round, we might have
never checked the fdTrigger. Ensure to check it at least once
before SSL_write / SSL_read.

Test: binderRpcTest
Bug: 190868302
Change-Id: I4588475354025f8f02d3eb998e9390d5babbc860
3 files changed