Always use global snap7 and modbus install

cli-client and diagnostic do not build yet. For cli client:

make: Entering directory '/home/bel/schwinn/lnx/git/silecs/silecs-cli-client'
rm -f build/bin/x86_64/silecs-cli-client
g++  -Isrc -std=c++11 -I../silecs-communication-cpp/build/include -I/usr/include/libxml2/ -I/acc/local/x86_64/3rdparty/boost/1.54.0/include -I/acc/local/x86_64/include -fPIC -g -Wall -Wno-long-long -Wconversion  -c -o bin/obj-src/silecs-cli-client/main.x86_64.o -MD -MP -MF bin/obj-src/silecs-cli-client/main.x86_64.d src/silecs-cli-client/main.cpp
g++  -o build/bin/x86_64/silecs-cli-client bin/obj-src/silecs-cli-client/main.x86_64.o -L/acc/local/x86_64/lib -Wl,-rpath-link,/acc/local/Linux/x86_64-linux-gcc/current/env/usr/lib64:/acc/local/Linux/x86_64-linux-gcc/current/env/lib64 -L/common/usr/cscofe/silecs/snap7/latest/lib/x86_64-linux -lsnap7 -L/usr/lib64 -lxml2 -L../silecs-communication-cpp/build/lib/x86_64 -lsilecs-comm -lstdc++ -lxml2 -lboost_system -lboost_filesystem  -lcurl -Wl,-rpath=/common/usr/cscofe/silecs/snap7/latest/lib/x86_64-linux  -lpthread
/bin/ld: cannot find -lsnap7