bmc-vmi-ca: use processs_loop

In reference [1], sdbusplus introduces its own process loop. This patch
removed the unncesssary sdeventplus dependency from bmc-vmi-ca, and uses
the sdbusplus built-in process loop instead.

[1] https://gerrit.openbmc.org/c/openbmc/sdbusplus/+/56891

Tested:
1. The daemon starts correctly
2. Tested several dbus commands via busctl (introspect, DeleteAll, etc)

Signed-off-by: Nan Zhou <nanzhoumails@gmail.com>
Change-Id: I802f18f077e7b0bd3bf0b910c56b1f560fe342e7
diff --git a/bmc-vmi-ca/mainapp.cpp b/bmc-vmi-ca/mainapp.cpp
index 062a60d..fc1c7af 100644
--- a/bmc-vmi-ca/mainapp.cpp
+++ b/bmc-vmi-ca/mainapp.cpp
@@ -2,7 +2,7 @@
 
 #include "ca_certs_manager.hpp"
 
-#include <sdeventplus/event.hpp>
+#include <sdbusplus/server/manager.hpp>
 #include <string>
 
 int main()
@@ -13,16 +13,10 @@
     // Add sdbusplus ObjectManager
     sdbusplus::server::manager_t objManager(bus, objPath);
 
-    // Get default event loop
-    auto event = sdeventplus::Event::get_default();
-
-    // Attach the bus to sd_event to service user requests
-    bus.attach_event(event.get(), SD_EVENT_PRIORITY_NORMAL);
-
     ca::cert::CACertMgr manager(bus, objPath);
 
     std::string busName = "xyz.openbmc_project.Certs.ca.authority.Manager";
     bus.request_name(busName.c_str());
-    event.loop();
+    bus.process_loop();
     return 0;
 }