fractional sizes discard with gcnv

[akalenyu]

Describe the bug
today gcnv completely discards fractional sizes
and picks the floor from the 1Gi aligment result
i.e. 10.6Gi results in 10Gi volume which does not satisfy the user request
example pod/pvc:

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: simple-pvc
spec:
  accessModes:
    - ReadWriteMany
  resources:
    requests:
      storage: 10.5Gi
---
apiVersion: v1
kind: Pod
metadata:
  creationTimestamp: null
  labels:
    run: test
  name: test
spec:
  securityContext:
    seccompProfile:
      type: RuntimeDefault
    runAsNonRoot: true
    runAsUser: 10001
    runAsGroup: 10001
    fsGroup: 10001
  containers:
  - image: quay.io/centos/centos:stream9
    command: ["/bin/bash"]
    args: ["-c", "sleep 3600000"]
    resources:
      limits:
        cpu: 750m
        memory: 600M
      requests:
        cpu: 100m
        memory: 60M
    name: test
    securityContext:
      allowPrivilegeEscalation: false
      capabilities:
        drop: ["ALL"]
    volumeMounts:
    - name: mypvc
      mountPath: /disk
  volumes:
  - name: mypvc
    persistentVolumeClaim:
      claimName: simple-pvc

bash-5.1$ df -B1 --output=avail /disk/
      Avail
10737156096

Environment
Provide accurate information about the environment to help us reproduce the issue.

• Trident version: [e.g. 19.10]
• Trident installation flags used: [e.g. -d -n trident --use-custom-yaml]
• Container runtime: [e.g. Docker 19.03.1-CE]
• Kubernetes version: [e.g. 1.15.1]
• Kubernetes orchestrator: [e.g. OpenShift v3.11, Rancher v2.3.3]
• Kubernetes enabled feature gates: [e.g. CSINodeInfo]
• OS: [e.g. RHEL 7.6, Ubuntu 16.04]
• NetApp backend types: [e.g. CVS for AWS, ONTAP AFF 9.5, HCI 1.7]
• Other:

To Reproduce
Steps to reproduce the behavior:

Expected behavior
A clear and concise description of what you expected to happen.

Additional context
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