http: fix drain event with cork/uncork #8282

Job	Run time
Build slim tarball	1m 38s
aarch64-linux: Cache V8 build	23s
aarch64-darwin: with shared libraries	23m 41s
x86_64-darwin: with shared libraries	36m 32s
x86_64-linux: with shared libraries	26m 40s
aarch64-linux: with shared boringssl-0.20260526.0	24m 19s
aarch64-linux: with shared openssl-3.0.20	24m 21s
aarch64-linux: with shared openssl-1.1.1w	22m 42s
aarch64-linux: with shared openssl-4.0.0	24m 15s
aarch64-linux: with shared openssl-3.6.2	23m 48s
aarch64-linux: with shared openssl-3.5.6	23m 28s
	3h 51m 47s

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