build+test+make: modify travis make directive to also compile sub-servers
build+test+make: modify travis make directive to also compile sub-servers

In this commit, we modify the travis make directive to also compile all
the sub-severs using build flags. We do this as otherwise, we can only
detect mistakes in the build process of a sub-server via a manual
process. In this commit, we adapt travis to also cover this case.

aakselrod/lnd,LightningNetwork/lnd,LightningNetwork/lnd,aakselrod/lnd