Log: libcrmcommon: Drop crm_perror() in pid.c

And improve error messages. errno is only specified as being set when
the return code is -1. So we don't want to log or return it for
incomplete writes.

The only added benefit of crm_perror() here is that it writes the
messages to stderr for crm_mon (the only caller of pcmkdaemonize(),
which in turn is the only caller of pcmklock_pidfile()). However,
no other PID-related errors or pcmkdaemonize() errors get written to
stderr, and CLI tools have verbose flags. So it doesn't seem worth the
hassle of passing a pcmkoutput_t object down the call chain.

(Interestingly, pcmk__daemonize() DOES log a couple of errors to
stdout.)

Ref T172

Signed-off-by: Reid Wahl <nrwahl@protonmail.com>