Check calloc() return value in nfsiostat and cifsiostat.

Check calloc() return value in nfsiostat and cifsiostat.

A call to calloc() function to allocate structures in nfsiostat and
cifsiostat wasn't checked for its return code. This call could possibly
fail without ever being noticed.

Mail from Ivana Varekova (varekova@redhat.com) 02/02/2011
Hello, I'm sending 6 patches - 3 for nfsiostat and 3 for cifsiostat
nfsiostat:
    nfsiostat2.patch - adds the forgotten test to malloc
(...)

cifsiostat:
    cifsiostat2.patch - adds the forgotten test to malloc
(...)