Change rpm dist packaging type for arm64 to aarch64 - same as goarch …

[sboeckelmann]

…arm64 but requires aarch64 rpm

Required for all PRs:

• Signed CLA.
• Associated README.md updated.
• Has appropriate unit tests.

[sboeckelmann]

Ok, this pull request pickup with your proposal from
#7630

Working nicely and package build for arm64 now results in:

[WARNING] run: Command 'git describe --exact-match --tags 2>/dev/null' failed with error: 
[INFO] print_banner: 
 _____     _                       __
/__   \___| | ___  __ _ _ __ __ _ / _|
  / /\/ _ \ |/ _ \/ _` | '__/ _` | |_
 / / |  __/ |  __/ (_| | | | (_| |  _|
 \/   \___|_|\___|\__, |_|  \__,_|_|
                  |___/
 Build Script

[INFO] check_environ: Checking environment...
[INFO] check_prereqs: Checking for dependencies...
[INFO] go_get: Retrieving dependencies...
[INFO] build: Starting build for linux/arm64...
[INFO] build: Using Go version: 1.13.4
[INFO] build: Using git branch: master
[INFO] build: Using git commit: 65c8f46283208e8ad2be11e4242ac4329181ecd9
[INFO] build: Sending build output to: /root/src/telegraf/build
[INFO] build: Using version 'None' for build.
[INFO] build: Building target: telegraf
[INFO] build: Time taken: 21.038154s
[INFO] package: Using temporary directory: /tmp/telegraf-build.62MCg0
[INFO] package: Creating packages for linux/arm64
[INFO] package_scripts: Copying scripts and configuration to build directory
[INFO] main: Packages created:
[INFO] main: telegraf_1.15.0~65c8f462-0_arm64.deb (SHA256=fea7f84a61e66991b7d8a1b4c61c194d11bf53d6910b65a1a897a9980c18fc6e)
[INFO] main: telegraf-1.15.0~65c8f462-0.aarch64.rpm (SHA256=fb8da56bb0919e08fdab44181a2b7e8059968285833558f93a14687421f4571c)
[INFO] main: telegraf-1.15.0~65c8f462_linux_arm64.tar.gz (SHA256=56d8a0fd2104b6672864b76595bd4a04cd6e81551f6ab7acc7c05b950417f593)