journal: bump RLIMIT_NOFILE when journal files to 16K (if possible)

When there are a lot of split out journal files, we might run out of fds
quicker then we want. Hence: bump RLIMIT_NOFILE to 16K if possible.

Do these even for journalctl. On Fedora the soft RLIMIT_NOFILE is at 1K,
the hard at 4K by default for normal user processes, this code hence
bumps this up for users to 4K.

https://bugzilla.redhat.com/show_bug.cgi?id=1179980

src/systemctl/systemctl.c

@@ -7409,6 +7409,11 @@ int main(int argc, char*argv[]) {
                 goto finish;
         }
 
+        /* Increase max number of open files to 16K if we can, we
+         * might needs this when browsing journal files, which might
+         * be split up into many files. */
+        setrlimit_closest(RLIMIT_NOFILE, &RLIMIT_MAKE_CONST(16384));
+
         if (!avoid_bus())
                 r = bus_open_transport_systemd(arg_transport, arg_host, arg_scope != UNIT_FILE_SYSTEM, &bus);