doveconf complains No matches on !include conf.d/* line but still writes out contents in conf.d

[runappz]

I'm on dovecot 2.3.3 (dcead646b). Output of `dovecot -n`:

# 2.3.3 (dcead646b): /etc/dovecot/dovecot.conf
# Pigeonhole version 0.5.3 (f018bbab)
doveconf: Fatal: Error in configuration file /etc/dovecot/dovecot.conf 
line 98: No matches
doveconf: Error: managesieve-login: dump-capability process returned 89
doveconf: Fatal: Error in configuration file /etc/dovecot/dovecot.conf 
line 98: No matches

While line 98 of dovecot.conf is just "!include conf.d/*.conf".

Output of `doveconf -n`:

# 2.3.3 (dcead646b): /etc/dovecot/dovecot.conf
# Pigeonhole version 0.5.3 (f018bbab)
doveconf: Fatal: Error in configuration file /etc/dovecot/dovecot.conf 
line 98: No matches
doveconf: Error: managesieve-login: dump-capability process returned 89
# OS: Linux 4.12.14-lp151.28.4-default x86_64
# Hostname: XXX
doveconf: Error: t_readlink(/var/run/dovecot/dovecot.conf) failed: 
readlink() failed: No such file or directory
namespace inbox {
............. (Removed for simplicity)
}
ssl = required
ssl_cert = </etc/postfix/ssl/certs/phys.cer
ssl_options = no_compression
ssl_prefer_server_ciphers = yes
userdb {
   driver = passwd
}

It's strange that all the extra content (especially ssl conf) only 
occurs in conf.d/10-ssl.conf.

To dig on what's happening underneath I ran `strace doveconf -n 2>&1 
|egrep "\.conf|conf\.d"` and got:

write(1, "# 2.3.3 (dcead646b): /etc/doveco"..., 47# 2.3.3 (dcead646b): 
/etc/dovecot/dovecot.conf
openat(AT_FDCWD, "/etc/dovecot/dovecot.conf", O_RDONLY) = 7
wait4(-1, doveconf: Fatal: Error in configuration file 
/etc/dovecot/dovecot.conf line 98: No matches
open("/etc/dovecot/conf.d", O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC) = 8
openat(AT_FDCWD, "/etc/dovecot/conf.d/90-sieve.conf", O_RDONLY) = 8
............. (Removed for simplicity)
openat(AT_FDCWD, "/etc/dovecot/conf.d/10-ssl.conf", O_RDONLY) = 20
openat(AT_FDCWD, "/etc/dovecot/conf.d/10-auth.conf", O_RDONLY) = 25
stat("/etc/dovecot/conf.d/auth-system.conf.ext", {st_mode=S_IFREG|0644, 
st_size=2182, ...}) = 0
openat(AT_FDCWD, "/etc/dovecot/conf.d/auth-system.conf.ext", O_RDONLY) = 26
stat("/etc/dovecot/local.conf", 0x7ffd94664760) = -1 ENOENT (No such 
file or directory)
stat("/etc/resolv.conf", {st_mode=S_IFREG|0644, st_size=709, ...}) = 0
open("/etc/host.conf", O_RDONLY|O_CLOEXEC) = 7
read(7, "#\n# /etc/host.conf - resolver co"..., 4096) = 370
open("/etc/resolv.conf", O_RDONLY|O_CLOEXEC) = 7
read(7, "### /etc/resolv.conf is a symlin"..., 4096) = 709
readlink("/var/run/dovecot/dovecot.conf", 0x5555db302598, 128) = -1 
ENOENT (No such file or directory)
write(2, "doveconf: Error: t_readlink(/var"..., 112doveconf: Error: 
t_readlink(/var/run/dovecot/dovecot.conf) failed: readlink() failed: No 
such file or directory

It seems that files in conf.d is never read before doveconf's complaint! 
I have totally no idea why this happens. Any help?