[BUG] flow controller

#### Expected behavior
if send flow failed the availablePermits should not be set to 0
Tell us what should happen
if send flow failed availablePermits should continue to add, then the next time we continue send flow , but now, we set availablePermits to 0, the next time we will not send flow, because conditions not satisfied, it maybe never send flow, then the 'select' will have no satisfied 'case', the process stuck.
#### Actual behavior

Tell us what happens instead

#### Steps to reproduce

How can we reproduce the issue
I think we should set availablePermits to 0 ,when send flow success.
#### System configuration
**Pulsar version**: 2.9.0

No file, test, or entry point is named. Start by locating the flow controller and tracing availablePermits through failed and successful send-flow paths in the Go client. Reproduce the stuck select behavior described for Pulsar 2.9.0, then add coverage showing permits remain available after failure and are cleared only after success.

Written by the indexing model from the issue text.