ENT-11166: Remove ShellCheck from centos-7, it is too old to work with our shellcheck annotations.

[craigcomstock]

Ticket: ENT-11166

[craigcomstock]

canary rhel-7 failed in nightlies, "fixed" this on the CI vms directly for now and we can regen them tomorrow

00:59:06 /usr/bin/shellcheck
00:59:06 ShellCheck - shell script analysis tool
00:59:06 version: 0.3.8
00:59:06 license: GNU General Public License, version 3
00:59:06 website: http://www.shellcheck.net/
00:59:06 
00:59:06 In cf-support line 386:
00:59:06 if [ -f $WORKDIR/share/cf-support-nova-hub.sh ]; then
00:59:06                                                  ^-- SC1009: The mentioned parser error was in this then clause.
00:59:06 
00:59:06 
00:59:06 In cf-support line 387:
00:59:06   # shellcheck source=/dev/null
00:59:06   ^-- SC1073: Couldn't parse this shellcheck annotation.
00:59:06                ^-- SC1072: Expected "disable". Fix any mentioned problems and try again.
00:59:06 
00:59:06 gmake[4]: *** [check-local] Error 1
00:59:06 gmake[3]: *** [check-am] Error 2