Improve log message for locksettings shell commands

Instead of the cryptic message "Caller pid %d Caller uid %d" at ERROR
level, use the clearer message "Executing shell command '%s';
callingPid=%d, callingUid=%d" at INFO level.  Intentionally log only the
command name, not the other arguments.  This is motivated by trying to
debug b/262185378.

Test: ran some shell commands and checked logcat
Bug: 262185378
Change-Id: Ibd0e2763deaedf0c12823aa890398a35e4c46d8d