os/bluestore: fix bluestore_wal_transaction_t encoding test

[tchaikov]

bluestore_wal_op_t::op is encoded/dumped but it is not
initialized in its ctor. so set it to 0 in its ctor. 0 is not an
valid op though, but it helps with debugging and testing.

Signed-off-by: Kefu Chai kchai@redhat.com

[tchaikov]

@liewegas this is a fix similar to 9ee941f

[ghost]

Reviewed-by: Loic Dachary <ldachary@redhat.com>

as soon as the make check returns on success.

[tchaikov]

@dachary it failed in

[ RUN      ] TestInternal.MultipleResize
./librbd/Journal.cc: In function 'void librbd::Journal< <template-parameter-1-1> >::handle_op_event_safe(int, uint64_t, const Future&, Context*) [with ImageCtxT = librbd::ImageCtx; uint64_t = long unsigned int; librbd::Journal< <template-parameter-1-1> >::Future = journal::Future]' thread 7f830e865700 time 2016-01-25 07:41:44.512447
./librbd/Journal.cc: 806: FAILED assert(m_state == STATE_READY || m_state == STATE_STOPPING)
 ceph version 10.0.2-1039-gefdc16d (efdc16d19d2d816668e174b50a9d1ab8fbfa9cb0)
 1: (ceph::__ceph_assert_fail(char const*, char const*, int, char const*)+0x8b) [0x7f8320ee715b]
 2: (librbd::Journal<librbd::ImageCtx>::handle_op_event_safe(int, unsigned long, journal::Future const&, Context*)+0x293) [0x7f8320bdb183]
 3: (Context::complete(int)+0x9) [0x7f8320b74339]
 4: (journal::FutureImpl::finish_unlock()+0x72) [0x7f8320e1b242]
 5: (journal::FutureImpl::C_ConsistentAck::complete(int)+0x12) [0x7f8320e1bf12]
 6: (Finisher::finisher_thread_entry()+0x206) [0x7f8320ec74f6]
 7: (()+0x7df5) [0x7f8316154df5]
 8: (clone()+0x6d) [0x7f831545f1ad]
 NOTE: a copy of the executable, or `objdump -rdS <executable>` is needed to interpret this.
./test/run-rbd-unit-tests.sh: line 10:  2257 Aborted                 RBD_FEATURES=$i unittest_librbd