Create a common function for git clone test related repos

[llxia]

In system tests and openjdk tests repos, we need to git clone and track repo sha.

aqa-tests/system/common.xml

Lines 51 to 93 in 9639787

	<getFileWithRetry file="STF" command="git clone -q ${stf_repo}" dest="${SYSTEMTEST_ROOT}"/>
	<echo message="git rev-parse ${stf_branch} "/>
	<exec executable="git" failonerror="false" dir="${SYSTEMTEST_ROOT}/STF" outputproperty="stf_sha1" resultproperty="code">
	<arg value="rev-parse"/>
	<arg value="${stf_branch}"/>
	</exec>
	<if>
	<equals arg1="${code}" arg2="128"/>
	<then>
	<echo message="git rev-parse origin/${stf_branch}"/>
	<exec executable="git" failonerror="true" dir="${SYSTEMTEST_ROOT}/STF" outputproperty="stf_sha2" resultproperty="code2">
	<arg value="rev-parse"/>
	<arg value="origin/${stf_branch}"/>
	</exec>
	<property name="stf_sha" value="${stf_sha2}"/>
	</then>
	</if>
	<if>
	<not>
	<isset property="stf_sha"/>
	</not>
	<then>
	<property name="stf_sha" value="${stf_sha1}"/>
	</then>
	</if>
	<if>
	<isset property="isZOS" />
	<then>
	<propertyregex
	property="stf_sha"
	input="${stf_sha}"
	regexp="\n"
	replace=""
	override="true"/>
	</then>
	</if>
	<echo message="git checkout -q -f ${stf_sha} "/>
	<exec executable="git" failonerror="true" dir="${SYSTEMTEST_ROOT}/STF" >
	<arg value="checkout"/>
	<arg value="-q"/>
	<arg value="-f"/>
	<arg value="${stf_sha}"/>
	</exec>

aqa-tests/openjdk/build.xml

Lines 86 to 128 in 9639787

	<getFileWithRetry file="openjdktemp" command="git clone --depth 1 -q ${REFERENCE_REPO} -b ${env.JDK_BRANCH} ${JDK_REPO_SPECIFIC} openjdktemp"/>
	<if>
	<equals arg1="${failCode}" arg2="128"/>
	<then>
	<getFileWithRetry file="openjdktemp" command="git clone -q ${JDK_REPO_SPECIFIC} openjdktemp"/>
	<echo message="git rev-parse ${env.JDK_BRANCH} "/>
	<exec executable="git" failonerror="false" dir="openjdktemp" outputproperty="jdk_sha1" resultproperty="code">
	<arg value="rev-parse"/>
	<arg value="${env.JDK_BRANCH}"/>
	</exec>
	<if>
	<equals arg1="${code}" arg2="128"/>
	<then>
	<echo message="git rev-parse origin/${env.JDK_BRANCH}"/>
	<exec executable="git" failonerror="true" dir="openjdktemp" outputproperty="jdk_sha2" resultproperty="code2">
	<arg value="rev-parse"/>
	<arg value="origin/${env.JDK_BRANCH}"/>
	</exec>
	<property name="jdk_sha" value="${jdk_sha2}"/>
	</then>
	</if>
	<if>
	<not>
	<isset property="jdk_sha"/>
	</not>
	<then>
	<property name="jdk_sha" value="${jdk_sha1}"/>
	</then>
	</if>
	<if>
	<isset property="isZOS"/>
	<then>
	<propertyregex property="jdk_sha" input="${jdk_sha}" regexp="\n" replace="" override="true"/>
	</then>
	</if>
	<echo message="git checkout -q -f ${jdk_sha} "/>
	<exec executable="git" failonerror="true" dir="openjdktemp">
	<arg value="checkout"/>
	<arg value="-q"/>
	<arg value="-f"/>
	<arg value="${jdk_sha}"/>
	</exec>
	</then>

We should create a common function for this.