pdump: fix error handlings

pdump: fix error handlings

The changes include
1)If mkdir fails for user passed socket paths log error and return.

2)At some places return value was set to errno and that non-negative number
was returned, but the intention was to return negative value.
So now rte_errno was set to errno and returning the actual negative value
that the APIs has returned.

Fixes: 278f945402c5 ("pdump: add new library for packet capture")

Signed-off-by: Reshma Pattan <reshma.pattan@intel.com>
Acked-by: Konstantin Ananyev <konstantin.ananyev@intel.com>