resource/random_password: Fix bcrypt_hash generation (#308)

Reference: #307

This change fixes the source of the `bcrypt_hash` generation to being the result of the random password generation. The issue was introduced in v3.4.0.

Previously:

```
--- FAIL: TestAccResourcePassword_BcryptHash (0.63s)
    /Users/bflad/src/github.com/hashicorp/terraform-provider-random/internal/provider/resource_password_test.go:107: Step 1/1 error: Check failed: Check 3/3 error: crypto/bcrypt: hashedPassword is not the hash of the given password
```

Suggested CHANGELOG:

```
NOTES:

* resource/random_password: If the resource was created between versions 3.4.0 and 3.4.2, the `bcrypt_hash` value would not correctly verify against the `result` value. Affected resources will automatically regenerate a valid `bcrypt_hash` after this upgrade.

BUG FIXES:

* resource/random_password: Fixed incorrect `bcrypt_hash` generation since version 3.4.0
```

internal/provider/provider_test.go

@@ -39,3 +39,12 @@ func providerVersion332() map[string]resource.ExternalProvider {
 		},
 	}
 }
+
+func providerVersion342() map[string]resource.ExternalProvider {
+	return map[string]resource.ExternalProvider{
+		"random": {
+			VersionConstraint: "3.4.2",
+			Source:            "hashicorp/random",
+		},
+	}
+}