Fix: Allow using boolean and integer as a value in with MM_* config helm parameters

[mike-code]

Fixes #238

Summary

This fix allows setting integers and booleans as values for helm parameters.

Description

Without this fix, using boolean as a value in any config.MM_* helm parameter would result in the following error

$ helm template my-setup . --set config.MM_SERVICESETTINGS_ENABLEAPIUSERDELETION="true"
Error: template: mattermost-team-edition/templates/secret-config.yaml:13:24: executing "mattermost-team-edition/templates/secret-config.yaml" at <b64enc>: wrong type for value; expected string; got bool

A workaround would be to wrap the quoted boolean in single quotes ie.

--set config.MM_SERVICESETTINGS_ENABLEAPIUSERDELETION='"true"'

however this environment variable would be rejected by the mattermost server and thus the user API deletion would still be disabled.

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[mattermost-build]

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[mike-code]

/check-cla