OCPBUGS-33024: agent: escape '%' in proxy settings

The 'DefaultEnvironment' config from systemd accepts some % specifiers
for expansion [1]. Because of that, proxy configurations that make use
of that character need to be escaped with another '%'.

[1] https://man7.org/linux/man-pages/man5/systemd-system.conf.5.html

Author: r4f4

data/data/agent/files/etc/systemd/system.conf.d/10-default-env.conf.template

@@ -1,12 +1,12 @@
 {{if .Proxy -}}
 [Manager]
 {{if .Proxy.HTTPProxy -}}
-DefaultEnvironment=HTTP_PROXY="{{.Proxy.HTTPProxy}}"
+DefaultEnvironment=HTTP_PROXY="{{replace .Proxy.HTTPProxy "%" "%%"}}"
 {{end -}}
 {{if .Proxy.HTTPSProxy -}}
-DefaultEnvironment=HTTPS_PROXY="{{.Proxy.HTTPSProxy}}"
+DefaultEnvironment=HTTPS_PROXY="{{replace .Proxy.HTTPSProxy "%" "%%"}}"
 {{end -}}
 {{if .Proxy.NoProxy -}}
 DefaultEnvironment=NO_PROXY="{{.Proxy.NoProxy}}"
 {{end -}}
-{{end -}}
+{{end -}}