Vagrant: Fix provisioning script

Add missing `make test-programs` step. Configure the number of
make jobs to match the number of vcpus.

Change-Id: I3a3547478a4043b46a941267bcfbaaef0fc7e552
Reviewed-on: https://code.wireshark.org/review/34579
Reviewed-by: João Valverde <j@v6e.pt>

vagrant_build.sh

@@ -15,5 +15,6 @@ grep -q WIRESHARK_BIN_DIR ~/.profile || echo "export WIRESHARK_BIN_DIR=~/build/r
 mkdir -p build
 cd build
 cmake -DENABLE_CCACHE=ON ../wireshark
-make -j6
+make -j4
+make test-programs
 make test