Fix net peer attribute for unix socket connection

[shadchin]

Description

After switch on .get(...), KeyError exception is never raised

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

import redis
from opentelemetry.instrumentation.redis import RedisInstrumentor

RedisInstrumentor().instrument()

client = redis.Redis(unix_socket_path="/foobar")  # or redis.Redis.from_url("unix:///foobar")
# Span attribute `net.peer.name` must be equal to `/foobar`

Does This PR Require a Core Repo Change?

• Yes. - Link to PR:
• No.

Checklist:

See contributing.md for styleguide, changelog guidelines, and more.

• Followed the style guidelines of this project
• Changelogs have been updated
• Unit tests have been added
• Documentation has been updated

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: shadchin / name: Alexander Shadchin (6ac715a, 3840fc5, 18a75d4)
• ✅ login: lzchen / name: Leighton Chen (34e3317)

[xrmx]

Thanks for the PR, please add a test so we can avoid regressions

[xrmx]

Thanks a lot for adding tests!

[xrmx]

@shadchin care to rebase and add a changelog entry please?