Test always evaluates the same

Defect 67272 (STATIC_C)
Checker DEADCODE (subcategory redundant_test)
File: /src/mongoc/mongoc-async-cmd.c
Function _mongoc_async_cmd_phase_send
/src/mongoc/mongoc-async-cmd.c, line: 280
Condition "bytes", taking false branch. Now the value of "bytes" is equal to 0.

       while (bytes) {

/src/mongoc/mongoc-async-cmd.c, line: 273
Condition "bytes < 0L", taking false branch. Now the value of "bytes" is at least 0.

       if (bytes < 0) {

/src/mongoc/mongoc-async-cmd.c, line: 292
At condition "bytes", the value of "bytes" must be equal to 0.

       if (!bytes) {

/src/mongoc/mongoc-async-cmd.c, line: 288
Assigning: "bytes" = "0L".

             bytes = 0;

/src/mongoc/mongoc-async-cmd.c, line: 292
The condition "!bytes" must be true.

       if (!bytes) {