NX-684: Registry root expiration fixes

Multiple problems fixes and improvements added:
* NX Core handled NPM MD as expired (as it sees it as coming from localstorage/cache)
* NPM Proxy MD service had a bug, that considered NPM reg root always as expired as it was incomplete
* improved logging with some TRACE logs
* added IT ensuring that once cached, registry root is not re-fetched
NX-684: Assure that registry root update does not happens concurrently
NX-684: fixing path recorder lifecycle

As it was created when mock registry was. Now it's re-created
per each start, to avoid possible interleaves of recorded data
from previous runs.
Merge pull request #18 from sonatype/NX-684-regroot-expiration

NX-684: Registry root expiration fixes