Fix nginxCloneScriptTemplate for old shells

[IldarMinaev]

dash version 0.5.10.2-5 return error for export command with spaces after = symbol:

# export qwe=nginx version: nginx/1.20.1
dash: 10: export: version:: bad variable name

Description:
Fixing bug with nginxCloneScriptTemplate on old shells.
In my case I have third-party docker image with nginx and dash Version: 0.5.10.2-5 as shell.
It return error:

# export NGINX_VERSION=$( { nginx -v ; } 2>&1 ) && echo ${NGINX_VERSION##*/} > /opt/opentelemetry-webserver/source-conf/version.txt
dash: 11: export: version:: bad variable name
# nginx -v 
nginx version: nginx/1.20.1
# export NGINX_VERSION=nginx version: nginx/1.20.1
dash: 13: export: version:: bad variable name
# 

I suggest to quote result of nginx-v command for set variable command.

Link to tracking Issue(s):

• Resolves: Nginx auto instrumentation failed to get nginx version on dash 0.5.10.2-5 #3651

Testing:
Run instrumentation of robotshop/rs-web:latest image.

Documentation:
N/A

[linux-foundation-easycla]

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• ✅ login: IldarMinaev (a803ee4, 118c91c)

[swiatekm]

The change itself looks fine to me, but ideally I'd like to add a e2e test to avoid regressions in the future. Is there a public nginx image using dash that we could use?

[IldarMinaev]

@swiatekm you can use robotshop/rs-web (part of https://github.com/instana/robot-shop). But it also has a problem with old version of Nginx (nginx:1.21.6) which is not supported by auto-instrumentation.