LU-6541 utils: fix potential memory leaks with realloc()

LU-6541 utils: fix potential memory leaks with realloc()

The semantics of realloc are to return NULL when the allocation fails,
but won't free the original allocation:

"The realloc() function returns a pointer to the newly allocated memory,
which is suitably aligned for any built-in type and may be different
from ptr, or NULL if the request fails. If size was equal to 0, either
NULL or a pointer suitable to be passed to free() is returned. If
realloc() fails, the original block is left untouched; it is not freed
or moved."

Signed-off-by: Dmitry Eremin <dmitry.eremin@intel.com>
Change-Id: Ib348acad13c866a2904e023ac5822f23d13b38ca
Reviewed-on: http://review.whamcloud.com/14814
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Bob Glossman <bob.glossman@intel.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>