[Ubuntu] Implement first Pester tests (#2270)

* implement first pester tests

* add comment for azcopy test

* remove extra importing and old function

* resolve comments

* fix typo

images/linux/scripts/tests/Tools.Tests.ps1

@@ -0,0 +1,17 @@
+Describe "7-Zip" {
+    It "7z" {
+        "7z" | Should -ReturnZeroExitCode
+    }
+}
+
+Describe "azcopy" {
+    It "azcopy" {
+        #(azcopy --version) command returns exit code 1 (see details: https://github.com/Azure/azure-storage-azcopy/releases)
+        $azcopyVersion = (Get-CommandResult "azcopy --version").Output
+        $azcopyVersion | Should -BeLike "*azcopy*"
+    }
+
+    It "azcopy10" {
+        "azcopy10 --version" | Should -ReturnZeroExitCode
+    }
+}