(Reuters) - Gunmen have ended a siege of Libya's foreign and justice ministries but the two-week standoff has left many unresolved questions about the government's ability to impose its authority in the capital, let alone the restive east of the country. The episode heightened security concerns that prompted oil group BP, one of the biggest foreign companies active in Libya, to announce on Sunday it was withdrawing an unspecified number of employees from Tripoli. The U.S. and British governments had already pulled out some diplomats temporarily. In a separate development, two more police stations were attacked in Libya's eastern city...