CCBC-1596: Fix compilation warning about lcb_PINGSVC struct

capi/cmd_ping.hh:129:15: warning: anonymous non-C-compatible type given name for linkage purposes by typedef declaration; add a tag name here [-Wnon-c-typedef-for-linkage]
typedef struct {
              ^
               lcb_PINGSVC
capi/cmd_ping.hh:132:23: note: type is not C-compatible due to this default member initializer
    const char *server{nullptr}; /**< server host:port */
                      ^~~~~~~~~
capi/cmd_ping.hh:139:3: note: type is given name 'lcb_PINGSVC' for linkage purposes by this typedef declaration
} lcb_PINGSVC;
  ^

Change-Id: I59876943063e810accf60b1263b5230ab08063e3
Reviewed-on: https://review.couchbase.org/c/libcouchbase/+/190107
Reviewed-by: Brett Lawson <brett19@gmail.com>
Reviewed-by: Trond Norbye <trond.norbye@couchbase.com>
Tested-by: Build Bot <build@couchbase.com>

Author: avsej

src/capi/cmd_ping.hh

@@ -126,7 +126,7 @@ struct lcb_CMDPING_ {
  *
  * @committed
  */
-typedef struct {
+typedef struct lcb_PINGSVC_ {
     lcb_PING_SERVICE type; /**< type of the service */
     /* TODO: rename to "remote" */
     const char *server{nullptr}; /**< server host:port */