Install script does not properly escape shell special characters in arguments

[ShylajaDevadiga]

Environmental Info:
K3s Version:
v1.20.5-alpha1+k3s2 (881500d)

Node(s) CPU architecture, OS, and Version:
Ubuntu 20.04

Cluster Configuration:
Single node server with etcd backend

Describe the bug:
While creating scheduled snapshot install script does not honor passing of '*' for the cron parameter

Steps To Reproduce:

1. Install k3s passing etcd snaphot flags as below with --etcd-snapshot-schedule-cron='*/1 * * * *'

curl -fL https://get.k3s.io | INSTALL_K3S_VERSION=v1.20.5-alpha1+k3s2 sh -s - server --cluster-init --etcd-s3 --etcd-s3-bucket=<bucket>  --etcd-snapshot-schedule-cron='*/1 * * * *'

2. Systemd unit file contains invalid entry for the cronjob value as */1 a snap a snap a snap *

cat /etc/systemd/system/k3s.service
[Unit]
Description=Lightweight Kubernetes
Documentation=https://k3s.io
Wants=network-online.target
After=network-online.target

[Install]
WantedBy=multi-user.target

[Service]
Type=notify
EnvironmentFile=/etc/systemd/system/k3s.service.env
KillMode=process
Delegate=yes
# Having non-zero Limit*s causes performance problems due to accounting overhead
# in the kernel. We recommend using cgroups to do container-local accounting.
LimitNOFILE=1048576
LimitNPROC=infinity
LimitCORE=infinity
TasksMax=infinity
TimeoutStartSec=0
Restart=always
RestartSec=5s
ExecStartPre=-/sbin/modprobe br_netfilter
ExecStartPre=-/sbin/modprobe overlay
ExecStart=/usr/local/bin/k3s \
    server \
	'--cluster-init' \
	'--etcd-s3' \
	'--etcd-s3-bucket=<bucket naame>' \
	'--etcd-snapshot-schedule-cron=*/1 a snap a snap a snap *' \

Expected behavior:
Regex should recognize * as a literal when passed within ''

Actual behavior:
Regex in install script does not recognize '*' as a literal passed to cron job and replaces with invalid value

NOTE: Snapshot/Restore functionality is working as expected when executing k3s binary with same flags.

[davidnuzik]

@brandond can review as he works on other install.sh script changes.

[davidnuzik]

Fixing milestone. Fixing issue state @cjellick

[ShylajaDevadiga]

Validated on v1.21.1+k3s1 shell special characters are interpreted correctly in the install script.