fix(cli-service): fix duplicate webpack-dev-server/client

[githoniel]

What kind of change does this PR introduce? (check at least one)

• Bugfix
• Feature
• Code style update
• Refactor
• Docs
• Underlying tools
• Other, please describe:

Does this PR introduce a breaking change? (check one)

• Yes
• No

Other information:

WebpackDevServer will add client scripts to entry by default, result in duplicate webpack-dev-server/client.

[pksunkara]

Can you describe a bit about why this is needed?

[githoniel]

@pksunkara
see https://github.com/webpack/webpack-dev-server/blob/v3.9.0/lib/utils/addEntries.js#L19

webpack-dev-server will add dev-entry-client and hot-entry when options.inline = true
in 3.9.0. Since vue-cli will add dev-entry-client and hot-entry manually, I set options.inline = false to avoid duplicate.

[sodatea]

inline: false only switches to iframe mode. The correct fix is to set injectClient: false, see #5069. It's been fixed in v4.2