Revert "Erase PST partition if its marked to be erased."

This now gets done at the framework level.
Doing it here breaks the signature on the partition.

This reverts commit ee19387905.

Bug: 19967123
Change-Id: I447b926b733ca145f11a916d9569ce39889db627

roots.cpp

@@ -39,8 +39,6 @@ static struct fstab *fstab = NULL;
 
 extern struct selabel_handle *sehandle;
 
-static const char* PERSISTENT_PATH = "/persistent";
-
 void load_volume_table()
 {
     int i;
@@ -266,41 +264,6 @@ int format_volume(const char* volume) {
     return -1;
 }
 
-int erase_persistent_partition() {
-    Volume *v = volume_for_path(PERSISTENT_PATH);
-    if (v == NULL) {
-        // most devices won't have /persistent, so this is not an error.
-        return 0;
-    }
-
-    int fd = open(v->blk_device, O_RDWR);
-    uint64_t size = get_file_size(fd);
-    if (size == 0) {
-        LOGE("failed to stat size of /persistent\n");
-        close(fd);
-        return -1;
-    }
-
-    char oem_unlock_enabled;
-    lseek(fd, size - 1, SEEK_SET);
-    read(fd, &oem_unlock_enabled, 1);
-
-    if (oem_unlock_enabled) {
-        if (wipe_block_device(fd, size)) {
-           LOGE("error wiping /persistent: %s\n", strerror(errno));
-           close(fd);
-           return -1;
-        }
-
-        lseek(fd, size - 1, SEEK_SET);
-        write(fd, &oem_unlock_enabled, 1);
-    }
-
-    close(fd);
-
-    return (int) oem_unlock_enabled;
-}
-
 int setup_install_mounts() {
     if (fstab == NULL) {
         LOGE("can't set up install mounts: no fstab loaded\n");