mdbx: backport - reset cursor EOF flag in cursor_set (ITS#8489).

It usually gets done anyway, but one of the fastpath shortcuts
bypassed this step.

Change-Id: I89d3c797ce969524e383b093dcf592579a514de1

mdb.c

@@ -6090,6 +6090,7 @@ mdb_cursor_set(MDB_cursor *mc, MDB_val *key, MDB_val *data,
 						}
 					}
 					rc = 0;
+					mc->mc_flags &= ~C_EOF;
 					goto set2;
 				}
 			}