minadbd: Support `adb reboot` under sideload/rescue modes.

Bug: 128415917
Test: Run the following commands under sideload and rescue modes
      respectively.
$ adb reboot
$ adb reboot bootloader
$ adb reboot recovery
$ adb reboot rescue
$ adb reboot invalid
Change-Id: I84daf63e3360b7b4a0af5e055149a4f54e10ba90
diff --git a/recovery_main.cpp b/recovery_main.cpp
index 37d9da0..0eb2962 100644
--- a/recovery_main.cpp
+++ b/recovery_main.cpp
@@ -477,6 +477,11 @@
         android::base::SetProperty(ANDROID_RB_PROPERTY, "reboot,bootloader");
         break;
 
+      case Device::REBOOT_RESCUE:
+        ui->Print("Rebooting to rescue...\n");
+        android::base::SetProperty(ANDROID_RB_PROPERTY, "reboot,rescue");
+        break;
+
       case Device::ENTER_FASTBOOT:
         if (logical_partitions_mapped()) {
           ui->Print("Partitions may be mounted - rebooting to enter fastboot.");