[Backport 2.6] Quote yugabyte gflag overrides

Summary:
In order to maintain compatibility with previous chart behavior, it's
necessary to quote gflag overrides in order to prevent breakages due to
multi-word gflag values.

This issue was introduced in 4e560f0

Test Plan:
Run template containing multi-word gflag value without this change:
$ helm install yugabyte ./ --set gflags.master.test1234="asdf asdf" --dry-run --debug
...
              --test1234=asdf asdf \
...

Run template contianing multi-word gflag value with this change:
$ helm install yugabyte ./ --set gflags.master.test1234="asdf asdf" --dry-run --debug
...
              --test1234="asdf asdf" \
...
Verify that the argument value is properly quoted.

Reviewers: sanketh

Reviewed By: sanketh

Subscribers: yugaware

Differential Revision: https://phabricator.dev.yugabyte.com/D12064

stable/yugabyte/templates/service.yaml

@@ -297,7 +297,7 @@ spec:
  --num_cpus={{ ceil $root.Values.resource.master.requests.cpu }} \
  --undefok=num_cpus,enable_ysql \
  {{- range $flag, $override := $root.Values.gflags.master }}
- --{{ $flag }}={{ $override }} \
+ --{{ $flag }}={{ quote $override }} \
  {{- end }}
  {{- if $root.Values.tls.enabled }}
  --certs_dir=/opt/certs/yugabyte \
@@ -346,7 +346,7 @@ spec:
  --use_cassandra_authentication=true \
  {{- end }}
  {{- range $flag, $override := $root.Values.gflags.tserver }}
- --{{ $flag }}={{ $override }} \
+ --{{ $flag }}={{ quote $override }} \
  {{- end }}
  {{- if $root.Values.tls.enabled }}
  --certs_dir=/opt/certs/yugabyte \