NEXUS-5898: Retry for LocalStorageEx too

As those might come from "real" local IO problem
(nx process unable to write to disk), but also from
remote IO problem, when the response body is attempted
to be read to have it cached/stored on disk.
NEXUS-5898: Related UT adjusted

The UT was wrong, it was shutting down remote server
(so the condition was met only once). But now
that remote problems will make Nx retry too,
the assertion was wrong.

UT adjusted that "remote server" always
consistently drop connection unexpectedly.
Merge pull request #170 from sonatype/NEXUS-5898-retries-conn-reset

NEXUS-5898: Retry for LocalStorageEx too