t/coverage.sh: Fall-back to lcov without --no-external.
t/coverage.sh: Fall-back to lcov without --no-external.

Old versions of lcov don't support that flag. Simply try to fall back in case
the first run fails.

tokkee/sysdb,tokkee/sysdb,sysdb/sysdb,tokkee/sysdb,sysdb/sysdb,sysdb/sysdb