ssl: fix SSLSocket#sysread leaking locktmp String on timeout #1291

Job	Run time
openssl-1.0.2u	51s
openssl-1.1.0l	53s
openssl-1.1.1w	56s
openssl-3.0.15	58s
openssl-3.1.7	1m 49s
openssl-3.2.3	1m 2s
openssl-3.3.2	1m 3s
openssl-3.4.0	1m 3s
openssl-master	3m 49s
libressl-3.1.5	1m 0s
libressl-3.2.7	1m 5s
libressl-3.3.6	59s
libressl-3.4.3	58s
libressl-3.5.3	1m 6s
libressl-3.6.3	1m 6s
libressl-3.7.3	57s
libressl-3.8.4	56s
libressl-3.9.2	1m 48s
libressl-4.0.0	58s
openssl-3.0.15 with fips provider	50s
openssl-3.1.7 with fips provider	48s
openssl-3.2.3 with fips provider	49s
openssl-3.3.2 with fips provider	50s
openssl-3.4.0 with fips provider	50s
openssl-master with fips provider	3m 39s
openssl-3.4.0 without legacy provider	56s
ruby-versions / Generate Ruby versions	2s
ubuntu-22.04 2.7	59s
ubuntu-22.04 3.0	52s
ubuntu-22.04 3.1	59s
ubuntu-22.04 3.2	56s
ubuntu-22.04 3.3	57s
ubuntu-22.04 head	1m 2s
ubuntu-22.04 truffleruby	1m 43s
ubuntu-22.04 truffleruby-head	1m 46s
ubuntu-20.04 2.7	1m 3s
ubuntu-20.04 3.0	54s
ubuntu-20.04 3.1	56s
ubuntu-20.04 3.2	57s
ubuntu-20.04 3.3	54s
ubuntu-20.04 head	56s
ubuntu-20.04 truffleruby	1m 36s
ubuntu-20.04 truffleruby-head	1m 47s
macos-latest 2.7	51s
macos-latest 3.0	34s
macos-latest 3.1	38s
macos-latest 3.2	36s
macos-latest 3.3	38s
macos-latest head	38s
macos-latest truffleruby	55s
macos-latest truffleruby-head	1m 17s
windows-latest 2.7	4m 48s
windows-latest 3.0	4m 23s
windows-latest 3.1	4m 13s
windows-latest 3.2	5m 21s
windows-latest 3.3	4m 33s
windows-latest head	3m 50s
windows-latest ucrt	4m 26s
windows-latest mswin	2m 35s
	1h 30m 34s

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