more notebook instance fixes (#3815) (#2332)

Signed-off-by: Modular Magician <[email protected]>

Author: modular-magician

.changelog/3815.txt

@@ -0,0 +1,3 @@
+```release-note:bug
+notebook: fixed bug where not setting `data_disk_type` or `disk_encryption` would cause a diff on the next plan
+```

google-beta/resource_notebooks_instance.go

@@ -146,18 +146,20 @@ You can choose the size of the data disk based on how big your notebooks and dat
 If not specified, this defaults to 100.`,
 			},
 			"data_disk_type": {
-				Type:         schema.TypeString,
-				Optional:     true,
-				ForceNew:     true,
-				ValidateFunc: validation.StringInSlice([]string{"DISK_TYPE_UNSPECIFIED", "PD_STANDARD", "PD_SSD", ""}, false),
-				Description:  `Possible disk types for notebook instances. Possible values: ["DISK_TYPE_UNSPECIFIED", "PD_STANDARD", "PD_SSD"]`,
+				Type:             schema.TypeString,
+				Optional:         true,
+				ForceNew:         true,
+				ValidateFunc:     validation.StringInSlice([]string{"DISK_TYPE_UNSPECIFIED", "PD_STANDARD", "PD_SSD", ""}, false),
+				DiffSuppressFunc: emptyOrDefaultStringSuppress("DISK_TYPE_UNSPECIFIED"),
+				Description:      `Possible disk types for notebook instances. Possible values: ["DISK_TYPE_UNSPECIFIED", "PD_STANDARD", "PD_SSD"]`,
 			},
 			"disk_encryption": {
-				Type:         schema.TypeString,
-				Optional:     true,
-				ForceNew:     true,
-				ValidateFunc: validation.StringInSlice([]string{"DISK_ENCRYPTION_UNSPECIFIED", "GMEK", "CMEK", ""}, false),
-				Description:  `Disk encryption method used on the boot and data disks, defaults to GMEK. Possible values: ["DISK_ENCRYPTION_UNSPECIFIED", "GMEK", "CMEK"]`,
+				Type:             schema.TypeString,
+				Optional:         true,
+				ForceNew:         true,
+				ValidateFunc:     validation.StringInSlice([]string{"DISK_ENCRYPTION_UNSPECIFIED", "GMEK", "CMEK", ""}, false),
+				DiffSuppressFunc: emptyOrDefaultStringSuppress("DISK_ENCRYPTION_UNSPECIFIED"),
+				Description:      `Disk encryption method used on the boot and data disks, defaults to GMEK. Possible values: ["DISK_ENCRYPTION_UNSPECIFIED", "GMEK", "CMEK"]`,
 			},
 			"install_gpu_driver": {
 				Type:     schema.TypeBool,