apphandler: Fix Device Revision being 0

If the Device Revision is set later, and therefore when convertVersion
returns a negative return value at ipmid startup, we shouldn't be
setting the `haveBMCVersion` flag. Only when the convertVersion returned
a non-negative value and we received a proper Device ID, should we
set the flag.

Tested:
At boot, with a platform with Device Revision 1,

Without the change:
~# ipmitool mc info
Device ID                 : 0
Device Revision           : 0
Firmware Revision         : 16.03

With the change:
~# ipmitool mc info
Device ID                 : 0
Device Revision           : 1
Firmware Revision         : 16.03

Signed-off-by: Brandon Kim <brandonkim@google.com>
Change-Id: Ia7a4e2d21384bb840a082d7ec91ad0ed1722c0c7
1 file changed