gnomekeyring: fix module loading
On GNU/Linux, g_module_open("libgnome-keyring", 0) searches for
libgnome-keyring.so, but most distributions install libraries with
versioned suffixes, like libgnome-keyring.so.0 or libgnome-keyring.so.1,
and thus the call (and whole plugin load) fails. For that reason, if
we can't find the library without suffix, try searching also for .so.0
or .so.1.