CI: travis-ci: replace not defined SSL_LIB, SSL_INC for BotringSSL builds

after 73b520b958be4ee79b4f09a32d6718a13dc2d1fd variables SSL_LIB, SSL_INC
are not set, but still used by BoringSSL builds. That leads to error
(I wish we could stop on such errors) and using stock openssl instead
of boringssl
1 file changed