Fix distro detection for SUSE Linux Enterprise

On SUSE Linux Enterprise distributions, lsb_release -i typically
returns "SUSE" not "SUSE LINUX" as the vendor string.

To avoid duplication of the same regular expressions in multiple
places, add is_opensuse() and is_sle() helper functions, and modify
is_suse to invoke those.

This may also be helpful in the future for distinguishing some corner
cases where things are handled differently between openSUSE and SLE.

Change-Id: I43bf163bc963758ddbb6289928837f5f6512f265

Author: Adam Spiers

functions-common

@@ -379,14 +379,14 @@ function GetDistro {
     elif [[ "$os_VENDOR" =~ (Fedora) ]]; then
         # For Fedora, just use 'f' and the release
         DISTRO="f$os_RELEASE"
-    elif [[ "$os_VENDOR" =~ (openSUSE) ]]; then
+    elif is_opensuse; then
         DISTRO="opensuse-$os_RELEASE"
         # Tumbleweed uses "n/a" as a codename, and the release is a datestring
         # like 20180218, so not very useful. Leap however uses a release
         # with a "dot", so for example 15.0
         [ "$os_CODENAME" = "n/a" -a "$os_RELEASE" = "${os_RELEASE/\./}" ] && \
             DISTRO="opensuse-tumbleweed"
-    elif [[ "$os_VENDOR" =~ (SUSE LINUX) ]]; then
+    elif is_suse_linux_enterprise; then
         # just use major release
         DISTRO="sle${os_RELEASE%.*}"
     elif [[ "$os_VENDOR" =~ (Red.*Hat) || \
@@ -460,11 +460,30 @@ function is_fedora {
 # (openSUSE, SLE).
 # is_suse
 function is_suse {
+    is_opensuse || is_suse_linux_enterprise
+}
+
+
+# Determine if current distribution is an openSUSE distribution
+# is_opensuse
+function is_opensuse {
+    if [[ -z "$os_VENDOR" ]]; then
+        GetOSVersion
+    fi
+
+    [[ "$os_VENDOR" =~ (openSUSE) ]]
+}
+
+
+# Determine if current distribution is a SUSE Linux Enterprise (SLE)
+# distribution
+# is_suse_linux_enterprise
+function is_suse_linux_enterprise {
     if [[ -z "$os_VENDOR" ]]; then
         GetOSVersion
     fi
 
-    [[ "$os_VENDOR" =~ (openSUSE) || "$os_VENDOR" == "SUSE LINUX" ]]
+    [[ "$os_VENDOR" =~ (^SUSE) ]]
 }