devmon: re-evaluate device conditions on reconf

Device conditions tracked by devmon were lost on `initctl reload`
because the reconf path did not re-assert them.  Add devmon_reconf()
to iterate all tracked device nodes and set or clear their conditions
based on current device presence.

Signed-off-by: Mattias Walström <lazzer@gmail.com>

src/devmon.h

@@ -27,6 +27,7 @@
 void devmon_add_cond(const char *cond);
 void devmon_del_cond(const char *cond);
 
+void devmon_reconf(void);
 void devmon_init(uev_ctx_t *ctx);
 
 #endif /* FINIT_DEVMON_H_ */