Last month, Maryland saw its strongest hiring since 2010, a sign the state’s long lackluster labor market may be starting to rev into motion. Employers added an estimated 11,000 jobs in December, driving the state’s unemployment rate down a tenth of a percentage point to 5.5 percent, according to U.S. Department of Labor data released Tuesday. Baltimore-area employers drove the upswing, adding an estimated 7,800 jobs.