CSTACKEX-299: validates the inputs for capacity bytes in update storage pool to be positive. (#101)

…r now validates inputs for positive number

### Description
validates the inputs for capacity bytes in update storage pool to be
positive.
This PR...
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### Types of changes

- [ ] Breaking change (fix or feature that would cause existing
functionality to change)
- [ ] New feature (non-breaking change which adds functionality)
- [X] Bug fix (non-breaking change which fixes an issue)
- [ ] Enhancement (improves an existing feature and functionality)
- [ ] Cleanup (Code refactoring and cleanup, that may add test cases)
- [ ] Build/CI
- [ ] Test (unit or integration test code)

### Feature/Enhancement Scale or Bug Severity

#### Feature/Enhancement Scale

- [ ] Major
- [ ] Minor

#### Bug Severity

- [ ] BLOCKER
- [ ] Critical
- [ ] Major
- [X] Minor
- [ ] Trivial

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### How Has This Been Tested?

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Author: sathvikaragi

api/src/main/java/org/apache/cloudstack/api/command/admin/storage/UpdateStoragePoolCmd.java

@@ -19,20 +19,20 @@
 import java.util.List;
 import java.util.Map;
 
-import org.apache.cloudstack.api.ApiCommandResourceType;
-
 import org.apache.cloudstack.api.APICommand;
+import org.apache.cloudstack.api.ApiArgValidator;
+import org.apache.cloudstack.api.ApiCommandResourceType;
 import org.apache.cloudstack.api.ApiConstants;
 import org.apache.cloudstack.api.ApiErrorCode;
 import org.apache.cloudstack.api.BaseCmd;
 import org.apache.cloudstack.api.Parameter;
 import org.apache.cloudstack.api.ServerApiException;
 import org.apache.cloudstack.api.response.StoragePoolResponse;
+import org.apache.commons.collections.MapUtils;
+import org.apache.commons.lang3.ObjectUtils;
 
 import com.cloud.storage.StoragePool;
 import com.cloud.user.Account;
-import org.apache.commons.collections.MapUtils;
-import org.apache.commons.lang3.ObjectUtils;
 
 @SuppressWarnings("rawtypes")
 @APICommand(name = "updateStoragePool", description = "Updates a storage pool.", responseObject = StoragePoolResponse.class, since = "3.0.0",
@@ -56,7 +56,7 @@ public class UpdateStoragePoolCmd extends BaseCmd {
     @Parameter(name = ApiConstants.CAPACITY_IOPS, type = CommandType.LONG, required = false, description = "IOPS CloudStack can provision from this storage pool")
     private Long capacityIops;
 
-    @Parameter(name = ApiConstants.CAPACITY_BYTES, type = CommandType.LONG, required = false, description = "Bytes CloudStack can provision from this storage pool")
+    @Parameter(name = ApiConstants.CAPACITY_BYTES, type = CommandType.LONG, required = false, description = "Bytes CloudStack can provision from this storage pool",validations={ApiArgValidator.PositiveNumber})
     private Long capacityBytes;
 
     @Parameter(name = ApiConstants.ENABLED, type = CommandType.BOOLEAN, required = false, description = "False to disable the pool for allocation of new volumes, true to" +