librbd/exclusive_lock/AcquireRequest.cc: init lock_type

Fixup for:

CID 1351687 (#1 of 1): Uninitialized scalar variable (UNINIT)
 var_decl: Declaring variable lock_type without initializer
 uninit_use: Using uninitialized value lock_type.

Signed-off-by: Danny Al-Gaaf <danny.al-gaaf@bisect.de>
(cherry picked from commit da9ede9)

src/librbd/exclusive_lock/AcquireRequest.cc

@@ -417,7 +417,7 @@ Context *AcquireRequest<I>::handle_get_lockers(int *ret_val) {
 
   std::map<rados::cls::lock::locker_id_t,
            rados::cls::lock::locker_info_t> lockers;
-  ClsLockType lock_type;
+  ClsLockType lock_type = LOCK_NONE;
   std::string lock_tag;
   if (*ret_val == 0) {
     bufferlist::iterator it = m_out_bl.begin();