init: error log on by-name identical replacement

The following message creates unnecessary alarm:

init: Partition system_a already existed in the by-name symlink map \
 with a value of \
 /dev/block/platform/soc/1d84000.ufshc/by-name/system_a, new value \
 /dev/block/platform/soc/1d84000.ufshc/by-name/system_a will be \
 ignored.

and in the code is cited as an ERROR.  The message admittedly does
point out an inefficiency by reporting multiple updates.

Test: compile
Change-Id: I388a76fa078cf9de5840930247f732d16ccb0719

Author: Mark Salyzyn

init/first_stage_mount.cpp

@@ -560,7 +560,7 @@ ListenerAction FirstStageMountVBootV2::UeventCallback(const Uevent& uevent) {
         std::vector<std::string> links = device_handler_->GetBlockDeviceSymlinks(uevent);
         if (!links.empty()) {
             auto [it, inserted] = by_name_symlink_map_.emplace(uevent.partition_name, links[0]);
-            if (!inserted) {
+            if (!inserted && (links[0] != it->second)) {
                 LOG(ERROR) << "Partition '" << uevent.partition_name
                            << "' already existed in the by-name symlink map with a value of '"
                            << it->second << "', new value '" << links[0] << "' will be ignored.";