monitor:  Allow missing presence property on start

During the initial boot where the fans aren't in inventory yet, if fan
monitor starts before fan presence then the Present property would not
be able to be read.  Catch that exception and let the code continue on
instead of crashing.

Signed-off-by: Matt Spinler <spinler@us.ibm.com>
Change-Id: Ief7527cfb3b2a921318d3775d3912a41b15444b1
1 file changed