tasks/lalinference.py: change naming convention of outputs from lalinference.
Previously the ouputs from lalinference had a prefix of LALInference.
.
This prefix was too long and caused a problem that the filename of a fits file
from an offline PE run exceeded the limit on the length of fits filename in GCN
Notices.
This naming convention change is also reflected in the pe tutorial https://git.ligo.org/pe/tutorials/merge_requests/49/.