StdLib/BsdSocketLib: Fix minor memory leak by freeing rrecp on error return.

StdLib/BsdSocketLib: Fix minor memory leak by freeing rrecp on error return.

The error return is triggered by one of two conditions:
  1.  rrecp is NULL (calloc failed)
  2.  strdup(dname) returns NULL

Previously, the function just returned NULL.  This patch adds a call to
free rrecp before returning NULL.  Since the free() function will properly
do nothing when called with a NULL parameter, it is not necessary to
separate the two tests into separate if clauses.

Reported-by: Colin King <colin.king@canonical.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Daryl McDaniel <edk2-lists@mc2research.org>
Reviewed-by: Jaben Carsey <jaben.carsey@intel.com>