Fixes a race condition when starting services in parallel with shepherd
0.10.x whereby a service might create files and directories with umask #o137.
An example is the bitlbee service with its least-authority wrapper: the
wrapper would create a tree with directories set to #o640, thereby
making the whole directory tree inaccessible.
* gnu/services/base.scm (syslog-shepherd-service): Pass #:file-creation-mask
to 'make-forkexec-constructor' instead of calling 'umask' in PID 1.
695042ff10