mdadm: Manage.c fix coverity issues

mdadm: Manage.c fix coverity issues

Fixing the following coding errors the coverity tools found:

* Event parameter_hidden:	declaration hides parameter "dv".
* Event leaked_storage: Variable "mdi" going out of scope leaks the storage
it points to.
* Event overwrite_var: Overwriting "mdi" in "mdi = mdi->devs" leaks the
storage that "mdi" points to.
* Event leaked_handle: Handle variable "lfd" going out of scope leaks
the handle.
* Event leaked_handle: Returning without closing handle "fd" leaks it.
* Event fixed_size_dest: You might overrun the 32-character fixed-sizei
string "devnm" by copying the return value of "fd2devnm" without
checking the length.
* Event fixed_size_dest: You might overrun the 32-character fixed-size
string "nm" by copying "nmp" without checking the length.
* Event fixed_size_dest: You might overrun the 32-character fixed-size
string "devnm" by copying the return value of "fd2devnm" without
checking the length.
* Event assigned_value: Assigning value "-1" to "tfd" here, but that
stored value is overwritten before it can be used.

Signed-off-by: Nigel Croxon <ncroxon@redhat.com>