Default service config not honored if initial name resolution fails

[temawi]

If the name resolution fails we are supposed to rely on the default service config since there is no way to get one via name resolution. This currently only happens if there has been at least one successful name resolution call. If the first name resolution fails, ManagedChannelImpl does not apply the service config.

• The default config is applied in NameResolverListener.onResult() when a successful response is retried
• In NameResolutionListener.onError() we do not apply the default service config.

[sergiitk]

Came out of #11018. May be full or partial solution for it.

[vinodhabib]

@kannanjgithub added the fix and writing the UT for the fix in progress

[vinodhabib]

@kannanjgithub PR raised for the Review, Request you to have a look once.

PR Link - #11368

[vinodhabib]

Completed Fix along with UT cases and PR got Approved.

[vinodhabib]

Got some more Review points recently from @ejona86 @kannanjgithub working on them.

[vinodhabib]

Fixed the recent review points and PR is ready for re-review.

[vinodhabib]

Fixed the Recent Review point and PR is Ready for Re-review

[ejona86]

@vinodhabib, please don't do those PR updates here. Do them on the PR.