tools: engine-setup - Fixed memory requirements

for running the engine, 4Gb is the minimum,
16Gb is the recomended ammount of RAM.

Change-Id: I4f439d41d76497cf5a69224ce257881d4ed23087
Bug-Url: https://bugzilla.redhat.com/921079
Signed-off-by: Sandro Bonazzola <sbonazzo@redhat.com>