MT#8125 run cron only on MGMT node

Change-Id: I59f7ee1b7af73102cdf151cd191ecbbab0b31e38
MT#8969 fix perl warnings:

Bareword file handle opened at line 28, column 1. See pages 202,204 of PBP. (Severity: 5)
Two-argument "open" used at line 28, column 1. See page 207 of PBP. (Severity: 5)
Integer with leading zeros: "0777" at line 285, column 48. See page 58 of PBP. (Severity: 5)
Integer with leading zeros: "0666" at line 309, column 46. See page 58 of PBP. (Severity: 5)

Two-argument "open" used at line 64, column 1. See page 207 of PBP. (Severity: 5)
Integer with leading zeros: "0666" at line 247, column 71. See page 58 of PBP. (Severity: 5)

Change-Id: Ic1eae412e4e39e8fd8a41537b9ecf846d4814f9a
MT#8969 Use Config::Simple to manage configs

fix perl warnings (both perl files):

Stricture disabled at line [37|73], column 9. See page 429 of PBP. (Severity: 5)

Change-Id: I2ffef64fef4e68ac9305e29da6c0743f00c25c1f
MT#8969 fix file permissions

Fixing regression from commit 2c31646:
mode "0644" sets mode to --w----r-T as perdoc -f chmod explains.
See PBP pages 58-59 for details.