build-unit-test-docker: Use newer lcov snapshot

lcov 1.13 is not compatible with gcc8 gcov results. This patch adds a
snapshot of lcov that is compatible with gcc8 instead of the ubuntu
provided vesion.

Change-Id: If475952a4059a3a17cc54cbc37feb664c0e831e7
Signed-off-by: William A. Kennington III <wak@google.com>
1 file changed