Only set oplog-reply flag on the oplog collection

Otherwise can crash mongod!

Wed Feb 26 11:09:32.829 [conn499]  logs.tmp-test-logs-10833_meteor_com Assertion failure str::startsWith(ns, "local.oplog.") src/mongo/db/repl_block.cpp 261
0x10b9245ab 0x10b8fb64c 0x10b816015 0x10b5b2d06 0x10b714ce6 0x10b6bf354 0x10b6c398b 0x10b4dd9e2 0x10b917699 0x10b957055 0x7fff948637a2 0x7fff948501e1
I20140226-11:09:32.831(-8) (satellite.js:296) process 85850 for job tmp-test-logs-10833.meteor.com null exited with 1
 0   mongod                              0x000000010b9245ab _ZN5mongo15printStackTraceERSo + 43
 1   mongod                              0x000000010b8fb64c _ZN5mongo12verifyFailedEPKcS1_j + 284
 2   mongod                              0x000000010b816015 _ZN5mongo19updateSlaveLocationERNS_5CurOpEPKcNS_6OpTimeE + 2405
 3   mongod                              0x000000010b5b2d06 _ZN5mongo12ClientCursor19updateSlaveLocationERNS_5CurOpE + 52
 4   mongod                              0x000000010b714ce6 _ZN5mongo14processGetMoreEPKcixRNS_5CurOpEiRbPb + 534
 5   mongod                              0x000000010b6bf354 _ZN5mongo15receivedGetMoreERNS_10DbResponseERNS_7MessageERNS_5CurOpE + 1492
 6   mongod                              0x000000010b6c398b _ZN5mongo16assembleResponseERNS_7MessageERNS_10DbResponseERKNS_11HostAndPortE + 4939
 7   mongod                              0x000000010b4dd9e2 _ZN5mongo16MyMessageHandler7processERNS_7MessageEPNS_21AbstractMessagingPortEPNS_9LastErrorE + 198
 8   mongod                              0x000000010b917699 _ZN5mongo17PortMessageServer17handleIncomingMsgEPv + 1657
 9   mongod                              0x000000010b957055 thread_proxy + 229
 10  libsystem_c.dylib                   0x00007fff948637a2 _pthread_start + 327
 11  libsystem_c.dylib                   0x00007fff948501e1 thread_start + 13