datatypes.c: Replace 'close' with 'closeData'

datatypes.c: Replace 'close' with 'closeData'

Older compilers fail to see that 'close' is not used a function
rather than a variable and produce the following error:

cc1: warnings being treated as errors
../../src/datatypes.c: In function 'virConnectCloseCallbackDataReset':
../../src/datatypes.c:149: error: declaration of 'close' shadows a global declaration [-Wshadow]

Replace all the 'close' occurrences with 'closeData' to resolve
this.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>