database/sql: add missing unlock when context is expired
database/sql: add missing unlock when context is expired

Missing the DB mutex unlock on an early return after checking
if the context has expired.

Fixes #17518

Change-Id: I247cafcef62623d813f534a941f3d5a3744f0738
Reviewed-on: https://go-review.googlesource.com/31494
Reviewed-by: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>
Run-TryBot: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>

polyverse-security/go,derekmarcotte/go,golang/go,josharian/go,derekmarcotte/go,Cofyc/go,goodlang/good,vsekhar/elastic-go,vsekhar/elastic-go,codestation/go,polyverse-security/go,cloudflare/go,suncycheng/go,nawawi/go,goodlang/good,vsekhar/elastic-go,codestation/go,cloudflare/go,akutz/go,momchil-velikov/go,polyverse-security/go,golang/go,ImJasonH/go,nawawi/go,momchil-velikov/go,goodlang/good,akutz/go,vsekhar/elastic-go,ImJasonH/go,linux-on-ibm-z/go,ImJasonH/go,cloudflare/go,CAFxX/go,vsekhar/elastic-go,derekmarcotte/go,codestation/go,linux-on-ibm-z/go,momchil-velikov/go,golang/go,polyverse-security/go,momchil-velikov/go,suncycheng/go,linux-on-ibm-z/go,codestation/go,Cofyc/go,josharian/go,christopher-henderson/Go,suncycheng/go,CAFxX/go,josharian/go,akutz/go,akutz/go,derekmarcotte/go,vsekhar/elastic-go,goodlang/good,josharian/go,ImJasonH/go,polyverse-security/go,akutz/go,goodlang/good,nawawi/go,suncycheng/go,suncycheng/go,akutz/go,derekmarcotte/go,derekmarcotte/go,Cofyc/go,Cofyc/go,codestation/go,momchil-velikov/go,linux-on-ibm-z/go,derekmarcotte/go,josharian/go,polyverse-security/go,cloudflare/go,ImJasonH/go,linux-on-ibm-z/go,ImJasonH/go,polyverse-security/go,nawawi/go,codestation/go,cloudflare/go,josharian/go,CAFxX/go,ImJasonH/go,akutz/go,momchil-velikov/go,nawawi/go,Cofyc/go,momchil-velikov/go,linux-on-ibm-z/go,josharian/go,suncycheng/go,CAFxX/go,vsekhar/elastic-go,golang/go,momchil-velikov/go,golang/go,golang/go,linux-on-ibm-z/go,Cofyc/go,golang/go,codestation/go,cloudflare/go,akutz/go,nawawi/go,CAFxX/go,polyverse-security/go,CAFxX/go,golang/go,suncycheng/go,goodlang/good,nawawi/go,josharian/go,codestation/go,CAFxX/go,goodlang/good,derekmarcotte/go,Cofyc/go,CAFxX/go,cloudflare/go,ImJasonH/go,Cofyc/go,cloudflare/go,vsekhar/elastic-go,goodlang/good,suncycheng/go,nawawi/go,linux-on-ibm-z/go