Use "command -v" instead of "which" to find path

If /usr/bin/which is not available, the current code
doesn't detect i.e. /usr/bin/zypper . Using "command -v" solved
the problem.

Change-Id: I1c281c3184d69cd9dc2418295b6a392d8e5693e0
diff --git a/functions-common b/functions-common
index d6e4663..0614b78 100644
--- a/functions-common
+++ b/functions-common
@@ -312,20 +312,20 @@
 # user if not available.  Note can't use generic install_package*
 # because they depend on this!
 function _ensure_lsb_release {
-    if [[ -x $(which lsb_release 2>/dev/null) ]]; then
+    if [[ -x $(command -v lsb_release 2>/dev/null) ]]; then
         return
     fi
 
-    if [[ -x $(which apt-get 2>/dev/null) ]]; then
+    if [[ -x $(command -v apt-get 2>/dev/null) ]]; then
         sudo apt-get install -y lsb-release
-    elif [[ -x $(which zypper 2>/dev/null) ]]; then
+    elif [[ -x $(command -v zypper 2>/dev/null) ]]; then
         # XXX: old code paths seem to have assumed SUSE platforms also
         # had "yum".  Keep this ordered above yum so we don't try to
         # install the rh package.  suse calls it just "lsb"
         sudo zypper -n install lsb
-    elif [[ -x $(which dnf 2>/dev/null) ]]; then
+    elif [[ -x $(command -v dnf 2>/dev/null) ]]; then
         sudo dnf install -y redhat-lsb-core
-    elif [[ -x $(which yum 2>/dev/null) ]]; then
+    elif [[ -x $(command -v yum 2>/dev/null) ]]; then
         # all rh patforms (fedora, centos, rhel) have this pkg
         sudo yum install -y redhat-lsb-core
     else