[Cherry-Pick][BugFix] prevent requests from entering running state without a slot (#7141)#7160

liyonghua0910 wants to merge 4 commits intoPaddlePaddle:release/2.4PaddlePaddle/FastDeploy:release/2.4from

liyonghua0910:release/2.4+20260402_fix_scheduleliyonghua0910/FastDeploy:release/2.4+20260402_fix_scheduleCopy head branch name to clipboard