The implementation of a cease-fire (and Lieberman's subsequent disapproval) indicate that Netanyahu is taking advice from the IDF rather than Lieberman, who is yet again contradicting the stated policy of his own government. The IDF realizes correctly that a second invasion of Gaza would be costly in terms of economic and political capital. It would also have much of the same mixed result as Operation Cast Lead in 2008-9. Some have tied the IDF's reaction to the Goldstone Report, but more likely the change come as a result of the IDF's own assessment.
In addition to considerations of basic military feasibility, Netanyahu is also dealing with uprisings across the Middle East, pressure to restart the peace process, and EU condemnation of settlements. Each of these issues translates to a need for Israel to not exacerbate its already strained relationship with the international community. There is no question that an invasion of Gaza would be severely limited by pressure from the international community to cease fire. By demonstrating restraint, Netanyahu is building trust which he can leverage for other issues.
Finally, the Israeli public is not exactly chomping at the bit to invade Gaza. Lieberman represents a loud minority, but a minority nonetheless. For pessimistic and war-weary Israelis, war would be a pointless exercise. It would also bring Tel Aviv, the Dan region, and Israel's population center into the war.