%memit: fix repeats for short-living statements

Based on the comment by leguyader:
#212 (comment)

Fixes #212

Author: vthriller

memory_profiler.py

@@ -1110,7 +1110,7 @@ def memit(self, line='', cell=None):
             counter += 1
             tmp = memory_usage((_func_exec, (stmt, self.shell.user_ns)),
                                timeout=timeout, interval=interval,
-                               max_usage=True,
+                               max_usage=True, max_iterations=1,
                                include_children=include_children)
             mem_usage.append(tmp)