Fix, skip FTP retry in certain cases

Fix, skip FTP retry in certain cases

In certain conditions there is no reason to retry fetching files.
For instance when the file is removed in the PNF or when
the password/certificate is wrong.

When the DFC is started there are always
queued VES events that referes to removed files which in turn results
in that the DFC will retry fetching these files in vain.
The DFC house keeps its number of concurrents tasks to not exeed quotas
for memory,open file descriptors etc.
As more threads are occupied with retrying, the fewer threads can do
their intended work, which decreases the throughput.

Testing has showed that already when the number of PNFs are 10, the throughput
is radically decreased (and the problem is then escalating).

Change-Id: I4833724a3ef3509025f4a0a438c6c8025932b0f4
Issue-ID: DCAEGEN2-1508
Signed-off-by: PatrikBuhr <patrik.buhr@est.tech>